Calculus Cheat Sheet
Limits
Definitions
Precise Definition : We say lim f (x) = L if for
Limit at Infinity : We say lim f (x) = L if we can
every ε > 0 there is a δ > 0 such that whenever
0 < |x − a| < δ then |f (x) − L| < ε.
make f (x) as close to L as we want by taking x
large enough and positive.
“Working” Definition : We say lim f (x) = L if
There is a similar definition for
we can make f (x) as close to L as we want by
taking x sufficiently close to a (on either side of a)
without letting x = a.
except we require x large and negative.
x→a
x→∞
x→a
lim f (x) = L
x→− ∞
Infinite Limit : We say lim f (x) = ∞ if we can
x→a
make f (x) arbitrarily large (and positive) by taking x
sufficiently close to a (on either side of a) without
letting x = a.
Right hand limit : lim f (x) = L. This has the
x→a+
same definition as the limit except it requires x > a.
Left hand limit : lim f (x) = L. This has the same There is a similar definition for lim f (x) = −∞
−
x→a
x→a
except we make f (x) arbitrarily large and negative.
definition as the limit except it requires x < a.
Relationship between the limit and one-sided limits
lim f (x) = L ⇒
x→a
lim f (x) = lim− f (x) = L ⇒
lim f (x) = lim− f (x) = L
x→a+
x→a+
x→a
lim f (x) 6= lim− f (x) ⇒
x→a+
x→a
x→a
lim f (x) = L
x→a
lim f (x)Does Not Exist
x→a
Properties
Assume lim f (x) and lim g(x) both exist and c is any number then,
x→a
x→a
lim f (x)
f (x)
1. lim [cf (x)] = c lim f (x)
4. lim
= x→a
provided lim g(x) 6= 0
x→a
x→a
x→a g(x)
x→a
lim g(x)
x→a
h
in
n
2. lim [f (x) ± g(x)] = lim f (x) ± lim g(x)
5.
lim
[f
(x)]
=
lim
f
(x)
x→a
x→a
x→a
x→a
3. lim [f (x)g(x)] = lim f (x) lim g(x)
x→a
x→a
x→a
x→a
hp
i q
6. lim n f (x) = n lim f (x)
x→a
x→a
Basic Limit Evaluations at ±∞
1. lim ex = ∞
&
x→∞
2. lim ln(x) = ∞
x→∞
lim
x→− ∞
&
ex = 0
lim ln(x) = −∞
5. n even :
6. n odd : lim xn = ∞
x→ ∞
x→0+
b
=0
x→∞ xr
7. n even :
3. If r > 0 then lim
r
4. If r > 0 and x is real for negative x
b
then lim
=0
x→− ∞ xr
lim xn = ∞
x→± ∞
&
lim
x→− ∞
xn = −∞
lim a xn + · · · + b x + c = sgn(a)∞
x→± ∞
8. n odd : lim a xn + · · · + b x + c = sgn(a)∞
x→∞
9. n odd :
lim a xn + · · · + c x + d = − sgn(a)∞
x→−∞
Note : sgn(a) = 1 if a > 0 and sgn(a) = −1 if a < 0.
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Calculus Cheat Sheet
Evaluation Techniques
Continuous Functions
L’Hospital’s/L’Hôpital’s Rule
If f (x)is continuous at a then lim f (x) = f (a)
x→a
x→a
Continuous Functions and Composition
f (x) is continuous at b and lim g(x) = b then
x→a
lim f (g(x)) = f lim g(x) = f (b)
x→a
x→a
Factor and Cancel
x2 + 4x − 12
(x − 2)(x + 6)
lim
= lim
x→2
x→2
x2 − 2x
x(x − 2)
= lim
x→2
x+6
8
= =4
x
2
Rationalize Numerator/Denominator
√
√
√
3− x
3− x 3+ x
√
lim 2
= lim 2
x→9 x − 81
x→9 x − 81 3 +
x
9−x
−1
√ = lim
√
x→9 (x2 − 81)(3 +
x) x→9 (x + 9)(3 + x)
= lim
=
If lim
f (x)
0
f (x)
±∞
= or lim
=
then,
x→a g(x)
g(x)
0
±∞
f (x)
f 0 (x)
= lim 0
, a is a number, ∞ or −∞
x→a g(x)
x→a g (x)
lim
Polynomials at Infinity
p(x) and q(x) are polynomials. To compute
p(x)
lim
factor largest power of x in q(x) out of
x→± ∞ q(x)
both p(x) and q(x) then compute limit.
x2 3 − x42
3x2 − 4
lim
= lim
x→− ∞ 5x − 2x2
x→− ∞ x2 5 − 2
x
=
3 − x42
3
=−
x→− ∞ 5 − 2
2
x
lim
Piecewise Function
lim g(x) where g(x) =
x→−2
−1
1
=−
(18)(6)
108
x2 + 5
1 − 3x
if x < −2
if x ≥ −2
Compute two one sided limits,
Combine Rational Expressions
1
1
1
1 x − (x + h)
lim
−
= lim
h→0 h
h→0 h
x+h x
x(x + h)
1
−h
−1
1
= lim
= lim
=− 2
h→0 h
h→0 x(x + h)
x(x + h)
x
lim g(x) =
x→−2−
lim g(x) =
x→−2+
lim x2 + 5 = 9
x→−2−
lim 1 − 3x = 7
x→−2+
One sided limits are different so lim g(x) doesn’t
x→−2
exist. If the two one sided limits had been equal
then lim g(x) would have existed and had the
x→−2
same value.
Some Continuous Functions
Partial list of continuous functions and the values of x for which they are continuous.
1. Polynomials for all x.
6. ln(x) for x > 0.
2. Rational function, except for x’s that give
division by zero.
√
3. n x (n odd) for all x.
√
4. n x (n even) for all x ≥ 0.
7. cos(x) and sin(x) for all x.
5. ex for all x.
8. tan(x) and sec(x) provided
3π π π 3π
x 6= · · · , − , − , ,
,···
2
2 2 2
9. cot(x) and csc(x) provided
x 6= · · · , −2π, −π, 0, π, 2π, · · ·
Intermediate Value Theorem
Suppose that f (x) is continuous on [a, b] and let M be any number between f (a) and f (b). Then there exists
a number c such that a < c < b and f (c) = M .
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Calculus Cheat Sheet
Derivatives
Definition and Notation
f (x + h) − f (x)
If y = f (x) then the derivative is defined to be f 0 (x) = lim
.
h→0
h
If y = f (x) then all of the following are equivalent
notations for the derivative.
df
dy
d
f 0 (x) = y 0 =
=
=
(f (x)) = Df (x)
dx
dx
dx
If y = f (x) all of the following are equivalent
notations for derivative evaluated at x = a.
df
dy
f 0 (a) = y 0 |x=a =
=
= Df (a)
dx x=a
dx x=a
Interpretation of the Derivative
If y = f (x) then,
1. m = f 0 (a) is the slope of the tangent line
to y = f (x) at x = a and the equation of
the tangent line at x = a is given by
y = f (a) + f 0 (a)(x − a).
2. f 0 (a) is the instantaneous rate of change of
f (x) at x = a.
3. If f (t) is the position of an object at time t then
f 0 (a) is the velocity of the object at t = a.
Basic Properties and Formulas
If f (x) and g(x) are differentiable functions (the derivative exists), c and n are any real numbers,
0
d 1.
c =0
4. f (x) ± g(x) = f 0 (x) ± g 0 (x)
dx
0
0
5. f (x) g(x) = f 0 (x) g(x) + f (x) g 0 (x) – Product Rule
2. c f (x) = c f 0 (x)
0
d n
f (x)
f 0 (x) g(x) − f (x) g 0 (x)
3.
x = n xn−1 – Power Rule
6.
=
– Quotient Rule
2
dx
g(x)
g(x)
d
7.
f g(x)
= f 0 g(x) g 0 (x) – Chain Rule
dx
d x =1
dx
d sin(x) = cos(x)
dx
d cos(x) = − sin(x)
dx
d tan(x) = sec2 (x)
dx
d sec(x) = sec(x) tan(x)
dx
Common Derivatives
d
csc(x) = − csc(x) cot(x)
dx
d cot(x) = − csc2 (x)
dx
d −1 1
sin (x) = √
dx
1 − x2
d 1
cos−1 (x) = − √
dx
1 − x2
d 1
tan−1 (x) =
dx
1 + x2
d x
a = ax ln(a)
dx
d x
e = ex
dx
1
d ln(x) = , x > 0
dx
x
d
1
ln |x| = , x 6= 0
dx
x
d 1
loga (x) =
, x>0
dx
x ln(a)
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Calculus Cheat Sheet
Chain Rule Variants
The chain rule applied to some specific functions.
in h
in−1
d h
1.
f (x)
= n f (x)
f 0 (x)
dx
d
f (x)
2.
e
= f 0 (x) ef (x)
dx
h
i f 0 (x)
d
3.
ln f (x) =
dx
f (x)
h
i
h
i
d
4.
sin f (x) = f 0 (x) cos f (x)
dx
d
dx
h
i
h
i
cos f (x) = −f 0 (x) sin f (x)
d
6.
dx
i
h
i
tan f (x) = f 0 (x) sec2 f (x)
d
dx
h
i
h
i
h
i
sec f (x) = f 0 (x) sec f (x) tan f (x)
d
8.
dx
5.
7.
h
−1
tan
h
i
f (x) =
f 0 (x)
h
i2
1 + f (x)
Higher Order Derivatives
The 2nd Derivative is denoted as
d2 f
f 00 (x) = f (2) (x) =
and is defined as
dx2
0
f 00 (x) = f 0 (x) , i.e. the derivative of the first
The nth Derivative is denoted as
dn f
f (n) (x) =
and is defined as
dxn
0
f (n) (x) = f (n−1) (x) , i.e. the derivative of the
derivative, f 0 (x).
(n − 1)st derivative, f (n−1) (x).
Implicit Differentiation
0
2x−9y
3 2
Find y if e
+ x y = sin(y) + 11x. Remember y = y(x) here, so products/quotients of x and y will use
the product/quotient rule and derivatives of y will use the chain rule. The “trick” is to differentiate as normal
and every time you differentiate a y you tack on a y 0 (from the chain rule). Then solve for y 0 .
e2x−9y (2 − 9y 0 ) + 3x2 y 2 + 2x3 y y 0 = cos(y)y 0 + 11
2e2x−9y − 9y 0 e2x−9y + 3x2 y 2 + 2x3 y y 0 = cos(y)y 0 + 11
2x3 y − 9e2x−9y − cos(y) y 0 = 11 − 2e2x−9y − 3x2 y 2
⇒
y0 =
11 − 2e2x−9y − 3x2 y 2
2x3 y − 9e2x−9y − cos(y)
Increasing/Decreasing – Concave Up/Concave Down
Critical Points
Concave Up/Concave Down
x = c is a critical point of f (x) provided either
1. If f 00 (x) > 0 for all x in an interval I then
f (x) is concave up on the interval I.
1. f 0 (c) = 0 or,
2. f 0 (c) doesn’t exist.
2. If f 00 (x) < 0 for all x in an interval I then
f (x) is concave down on the interval I.
Increasing/Decreasing
1. If f 0 (x) > 0 for all x in an interval I then
f (x) is increasing on the interval I.
0
2. If f (x) < 0 for all x in an interval I then
Inflection Points
x = c is a inflection point of f (x) if the
concavity changes at x = c.
f (x) is decreasing on the interval I.
3. If f 0 (x) = 0 for all x in an interval I then
f (x) is constant on the interval I.
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Calculus Cheat Sheet
Extrema
Absolute Extrema
Relative (local) Extrema
1. x = c is an absolute maximum of f (x) if
f (c) ≥ f (x) for all x in the domain.
1. x = c is a relative (or local) maximum of f (x)
if f (c) ≥ f (x) for all x near c.
2. x = c is an absolute minimum of f (x) if
f (c) ≤ f (x) for all x in the domain.
2. x = c is a relative (or local) minimum of f (x)
if f (c) ≤ f (x) for all x near c.
Fermat’s Theorem
1st Derivative Test
If f (x) has a relative (or local) extrema at x = c,
then x = c is a critical point of f (x).
If x = c is a critical point of f (x) then x = c is
1. a relative maximum of f (x) if f 0 (x) > 0 to the
left of x = c and f 0 (x) < 0 to the right of x = c.
Extreme Value Theorem
If f (x) is continuous on the closed interval [a, b] then
there exist numbers c and d so that,
2. a relative minimum of f (x) if f 0 (x) < 0 to the
left of x = c and f 0 (x) > 0 to the right of x = c.
3. not a relative extrema of f (x) if f 0 (x is the
1. a ≤ c, d ≤ b,
same sign on both sides of x = c.
2. f (c) is the absolute maximum in [a, b],
3. f (d) is the absolute minimum in [a, b].
2nd Derivative Test
Finding Absolute Extrema
To find the absolute extrema of the continuous
function f (x) on the interval [a, b] use the following
process.
1. Find all critical points of f (x) in [a, b].
If x = c is a critical point of f (x) such that f 0 (c) = 0
then x = c
1. is a relative maximum of f (x) if f 00 (c) < 0.
2. is a relative minimum of f (x) if f 00 (c) > 0.
3. may be a relative maximum, relative
2. Evaluate f (x) at all points found in Step 1.
minimum, or neither if f 00 (c) = 0.
3. Evaluate f (a) and f (b).
4. Identify the absolute maximum (largest
function value) and the absolute minimum
(smallest function value) from the
evaluations in Steps 2 & 3.
Finding Relative Extrema and/or
Classify Critical Points
1. Find all critical points of f (x).
2. Use the 1st derivative test or the
2nd derivative test on each critical point.
Mean Value Theorem
If f (x) is continuous on the closed interval [a, b] and differentiable on the open interval (a, b) then there is a
f (b) − f (a)
number a < c < b such that f 0 (c) =
.
b−a
Newton’s Method
If xn is the nth guess for the root/solution of f (x) = 0 then (n + 1)st guess is xn+1 = xn −
f 0 (xn ) exists.
© Paul Dawkins - https://tutorial.math.lamar.edu
f (xn )
provided
f 0 (xn )
Calculus Cheat Sheet
Related Rates
Sketch picture and identify known/unknown quantities. Write down equation relating quantities and differentiate with respect to t using implicit differentiation (i.e. add on a derivative every time you differentiate a
function of t). Plug in known quantities and solve for the unknown quantity.
Example A 15 foot ladder is resting against a
wall. The bottom is initially 10 ft away and is being
pushed towards the wall at 14 ft/sec. How fast is the
top moving after 12 sec?
x0 is negative because x is decreasing.
Pythagorean Theorem and differentiating,
Using
2x x0 + 2y y 0 = 0
After 12 sec we have x = 10 − 12 14 = 7 and so
p
√
y = 152 − 72 = 176. Plug in and solve for y 0 .
√
1
7
7 −
+ 176 y 0 = 0 ⇒ y 0 = √
ft/sec
4
4 176
x2 + y 2 = 152
⇒
Example Two people are 50 ft apart when one
starts walking north. The angle θ changes at
0.01 rad/min. At what rate is the distance between
them changing when θ = 0.5 rad?
We have θ0 = 0.01 rad/min. and want to find x0 . We
can use various trig functions but easiest is,
x
x0
sec(θ) =
⇒ sec(θ) tan(θ) θ0 =
50
50
We know θ = 0.5 so plug in θ0 and solve.
x0
sec(0.5) tan(0.5) (0.01) =
50
x0 = 0.3112 ft/min
Remember to have calculator in radians!
Optimization
Sketch picture if needed, write down equation to be optimized and constraint. Solve constraint for one of
the two variables and plug into first equation. Find critical points of equation in range of variables and verify
that they are min/max as needed.
Example We’re enclosing a rectangular field with
500 ft of fence material and one side of the field is a
building. Determine dimensions that will maximize
the enclosed area.
Maximize A = xy subject to constraint x+2y = 500.
Solve constraint for x and plug into area.
x = 500 − 2y
⇒
Example Determine point(s) on y = x2 + 1 that are
closest to (0, 2).
Minimize f = d2 = (x − 0)2 + (y − 2)2 and the
constraint is y = x2 + 1. Solve constraint for x2 and
plug into the function.
x2 = y − 1 ⇒ f = x2 + (y − 2)2
A = y(500 − 2y)
= 500y − 2y 2
= y − 1 + (y − 2)2 = y 2 − 3y + 3
Differentiate and find critical point(s).
Differentiate and find critical point(s).
f 0 = 2y − 3
A0 = 500 − 4y ⇒ y = 125
By the 2nd derivative test this is a relative minimum
and so all we need to do is find x value(s).
By 2nd derivative test this is a relative maximum and
so is the answer we’re after. Finally, find x.
x = 500 − 2(125) = 250
The dimensions are then 250 x 125.
−1=
1
2
y=
3
2
x = ± √12
The 2 points are then √12 , 32 and − √12 , 32 .
x2 =
3
2
⇒
⇒
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Calculus Cheat Sheet
Integrals
Definitions
Definite Integral : Suppose f (x) is continuous on
[a, b]. Divide [a, b] into n subintervals of width ∆ x
and choose x∗i from each interval. Then
Z b
n
X
f (x) dx = lim
f (x∗i ) ∆ x.
n→∞
a
Anti-Derivative : An anti-derivative of f (x) is a
function, F (x), such that F 0 (x) = f (x).
Z
Indefinite Integral :
f (x) dx = F (x) + c where
F (x) is an anti-derivative of f (x).
i=1
Fundamental Theorem of Calculus
Part I : If f (x) is continuous on [a, b] then
Z x
g(x) =
f (t) dt is also continuous on [a, b] and
Variants of Part I :
Z u(x)
d
f (t) dt = u0 (x)f u(x)
dx a
Z b
d
f (t) dt = −v 0 (x)f v(x)
dx v(x)
a
g 0 (x) =
d
dx
Z
x
f (t) dt = f (x).
a
Part II : f (x) is continuous on [a, b], F (x) is an
Z
anti-derivative of f (x), i.e. F (x) = f (x) dx, then
Z b
f (x) dx = F (b) − F (a).
Z
d
dx
u(x)
f (t) dt = u0 (x)f u(x) − v 0 (x)f v(x)
v(x)
a
Z
Z
f (x) ± g(x) dx =
Z
f (x) dx ±
b
Z
f (x) ± g(x) dx =
a
Z
Properties
Z
Z
cf (x) dx = c f (x) dx, c is a constant
Z
g(x) dx
b
b
Z
f (x) dx ±
a
a
a
a
b
Z
c dx = c(b − a), c is a constant
a
b
a
Z
f (x) dx = −
Z
b
b
Z
f (x) dx =
c
Z
a
b
f (x) dx
a
b
Z
f (x) dx for any value c.
f (x) dx +
a
b
f (x) dx ≤
f (x) dx
a
a
f (x) dx, c is a constant
a
a
Z
b
Z
cf (x) dx = c
f (x) dx = 0
Z
b
Z
g(x) dx
c
Z
If f (x) ≥ g(x) on a ≤ x ≤ b then
b
Z
a
Z
If f (x) ≥ 0 on a ≤ x ≤ b then
b
f (x) dx ≥
g(x) dx
a
b
f (x) dx ≥ 0
a
Z
If m ≤ f (x) ≤ M on a ≤ x ≤ b then m(b − a) ≤
b
f (x) dx ≤ M (b − a)
a
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Calculus Cheat Sheet
Common Integrals
Z
Z
k dx = k x + c
Z
Z
eu du = eu + c
Z
1
1
dx = ln |ax + b| + c
ax + b
a
Z
csc2 (u) du = − cot(u) + c
u Substitution :
dx =
1
dx = ln |x| + c
x
tan(u) du = ln |sec(u)| + c
Z
csc(u) cot(u)du = − csc(u) + c
R
sec(u)du =
ln sec(u) + tan(u) + c
R
csc(u)du =
− ln csc(u) + cot(u) + c
sec (u) du = tan(u) + c
Z
ln(u) du = u ln (u) − u + c
Z
2
−1
Z
sin(u) du = − cos(u) + c
Z
x
sec(u) tan(u) du = sec(u) + c
Z
Z
Z
Z
cos(u) du = sin(u) + c
Z
1
x dx =
xn+1 + c, n 6= −1
n+1
n
tan(u) du = − ln |cos(u)| + c
Z
1
1
−1 u
du
=
tan
+c
a2 + u2
a
a
Z
u
1
√
du = sin−1
+c
a
a2 − u2
Standard Integration Techniques
Z b
Z
b
0
0
f (g(x)) g (x) dx will convert the integral into
f (g(x)) g (x) dx =
a
a
g(b)
f (u) du using
g(a)
the substitution u = g(x) where du = g 0 (x)dx. For indefinite integrals drop the limits of integration.
Z
Example
2
1
u=x
3
x=1
2
Z
5x2 cos x3 dx
5x2 cos x3 dx =
1
1
⇒ du = 3x dx ⇒ x dx = du
3
⇒ u = 13 = 1 :: x = 2 ⇒ u = 23 = 8
2
2
=
5
sin(u)
3
8
1
Z
8
5
cos(u) du
1 3
5
=
sin(8) − sin(1)
3
Products and (some) Quotients of Trig Functions
R
R
For sinn (x) cosm (x) dx we have the following :
For tann (x) secm (x) dx we have the following :
1. n odd. Strip 1 sine out and convert rest to
1. n odd. Strip 1 tangent and 1 secant out and
cosines using sin2 (x) = 1 − cos2 (x), then use
convert the rest to secants using
the substitution u = cos(x).
tan2 (x) = sec2 (x) − 1, then use the
2. m odd. Strip 1 cosine out and convert rest to
substitution u = sec(x).
sines using cos2 (x) = 1 − sin2 (x), then use
2. m even. Strip 2 secants out and convert rest
the substitution u = sin(x).
to tangents using sec2 (x) = 1 + tan2 (x), then
3. n and m both odd. Use either 1. or 2.
use the substitution u = tan(x).
4. n and m both even. Use double angle
3. n odd and m even. Use either 1. or 2.
and/or half angle formulas to reduce the
4. n even and m odd. Each integral will be
integral into a form that can be integrated.
dealt with differently.
Trig Formulas : sin(2x) = 2 sin(x) cos(x), cos2 (x) = 12 (1 + cos(2x)), sin2 (x) = 12 (1 − cos(2x))
Z
Z
sin5 (x)
3
5
Example tan (x) sec (x) dx
Example
cos3 (x) dx
Z
Z
Z
Z
Z
(sin2 x)2 sin x
sin5 x
sin4 x sin x
tan3 x sec5 x dx = tan2 x sec4 x tan x sec x dx
dx
=
dx
=
dx
cos3 x
cos3 x
cos3 x
Z
Z
h
i
(1−cos2 (x))2 sin(x)
=
sec2 (x) − 1 sec4 (x) tan(x) sec(x)dx
=
dx
u
=
cos(x)
3
cos (x)
Z
h
i
Z
Z
4
2 2
2
)
1−2u2 +u4
=
u − 1 u du
u = sec(x)
= − (1−u
du
=
−
du
u3
u3
=
1
7
sec7 (x) −
1
5
sec5 (x) + c
=
1
2
sec2 (x) + 2 ln cos(x) −
© Paul Dawkins - https://tutorial.math.lamar.edu
1
2
cos2 (x) + c
Calculus Cheat Sheet
Z b
b
u dv = uv −
v du. Choose u and dv from integral
a
a
Ra
and compute du by differentiating u and compute v using v = dv.
Z
Z 5
Example xe−x dx
Example
ln(x) dx
Z
Integration by Parts :
Z
u dv = uv −
Z
b
v du and
3
−x
u
⇒ Zdu = dx v = −e−x
Z = x dv = e
xe−x dx = −xe−x + e−x dx
u = ln(x) dv = dx ⇒ du = x1 dx v = x
Z 5
Z 5
5
ln(x) dx = x ln(x) −
dx = (x ln(x) − x)
3
= −xe−x − e−x + c
3
3
5
3
= 5 ln(5) − 3 ln(3) − 2
Trig Substitutions : If the integral contains the following root use the given substitution and formula to
convert into an integral involving trig functions.
p
p
p
a2 − b2 x2 ⇒ x = ab sin(θ)
b2 x2 − a2 ⇒ x = ab sec(θ)
a2 + b2 x2 ⇒ x = ab tan θ
cos2 (θ) = 1 − sin2 (θ)
tan2 (θ) = sec2 (θ) − 1
sec2 (θ) = 1 + tan2 (θ)
Z
Z
Z
16
16
12
2
√
Example
dx
dθ
2
3 cos θ dθ =
4
2
2
x 4 − 9x
sin2 (θ)
9 sin (θ)(2 cos θ)
Z
x = 23 sin(θ) ⇒ dx = 23 cos(θ) dθ
= 12 csc2 (θ)dθ = −12 cot(θ) + c
q
p
p
4 − 9x2 = 4 − 4 sin2 (θ) = 4 cos2 (θ) = 2 |cos(θ)|
Use Right Triangle Trig to go back to x’s. From
√
Recall x2 = |x|. Because we have an indefinite
substitution we have sin(θ) = 3x
2 so,
integral we’ll assume positive and drop absolute
value bars. If we had a definite integral we’d need to
compute θ’s and remove absolute value bars based
on that and,
√
2
x if x ≥ 0
From this we see that cot(θ) = 4−9x
. So,
3x
|x| =
√
−x if x < 0
Z
16
4 4 − 9x2
p
√
dx
=
−
+c
x
In this case we have 4 − 9x2 = 2 cos(θ).
x2 4 − 9x2
R P (x)
Partial Fractions : If integrating a rational expression involving polynomials, Q(x)
dx, where the degree of
P (x) is smaller than the degree of Q(x). Factor denominator as completely as possible and find the partial
fraction decomposition of the rational expression. Integrate the partial fraction decomposition (P.F.D.). For
each factor in the denominator we get term(s) in the decomposition according to the following table.
Factor of Q(x)
ax + b
ax2 + bx + c
Term in P.F.D
A
ax + b
Ax + B
ax2 + bx + c
Factor is Q(x)
(ax + b)k
(ax2 + bx + c)k
7x2 + 13x
Example
dx
(x − 1) (x2 +Z4)
Z
2
7x + 13x
4
3x + 16
dx =
+ 2
dx
2
(x − 1) (x + 4)
x−1
x +4
Z
4
3x
16
=
+
+
dx
x − 1 x2 + 4 x2 + 4
= 4 ln |x − 1| + 32 ln x2 + 4 + 8tan−1 x2
Z
Here is partial fraction form and recombined.
Term in P.F.D
A1
A2
Ak
+
+ ··· +
ax + b (ax + b)2
(ax + b)k
A1 x + B 1
Ak x + Bk
+ ··· +
2
ax + bx + c
(ax2 + bx + c)k
7x2 +13x
(x−1) (x2 +4)
=
A
x−1
+
Bx+C
x2 +4
=
A(x2 +4)+(Bx+C) (x−1)
(x−1) (x2 +4)
Set numerators equal and collect like terms.
7x2 + 13x = (A + B) x2 + (C − B) x + 4A − C
Set coefficients equal to get a system and solve to
get constants.
A + B = 7 C − B = 13 4A − C = 0
A=4
B=3
C = 16
© Paul Dawkins - https://tutorial.math.lamar.edu
Calculus Cheat Sheet
Applications of Integrals
Z
Net Area :
b
f (x) dx represents the net area between f (x) and
a
the x-axis with area above x-axis positive and area below x-axis negative.
Area Between Curves : The general formulas for the two main cases for each are,
Z b
Z d
y = f (x) ⇒ A =
[upper function] − [lower function] dx & x = f (y) ⇒ A =
[right function] − [left function] dy
a
c
If the curves intersect then the area of each portion must be found individually. Here are some sketches of
a couple possible situations and formulas for a couple of possible cases.
b
Z
d
Z
f (x) − g(x) dx
A=
a
c
Z
f (y) − g(y) dy
A=
c
b
Z
f (x) − g(x) dx +
A=
a
g(x) − f (x) dx
c
R
R
Volumes of Revolution : The two main formulas are V = A(x) dx and V = A(y) dy. Here is some
general information about each method of computing and some examples.
Cylinders/Shells
Rings
2
2
A = π (outer radius) − (inner radius)
A = 2π(radius)(width / height)
Limits: x/y of right/bot ring to x/y of left/top ring
Horz. Axis use f (x),
g(x), A(x) and dx.
Vert. Axis use f (y),
g(y), A(y) and dy.
Limits : x/y of inner cyl. to x/y of outer cyl.
Horz. Axis use f (y),
Vert. Axis use f (x),
g(y), A(y) and dy.
g(x), A(x) and dx.
Ex. Axis : y = a > 0
Ex. Axis : y = a ≤ 0
Ex. Axis : y = a > 0
Ex. Axis : y = a ≤ 0
outer radius : a − f (x)
outer radius: |a| + g(x)
radius : a − y
radius : |a| + y
inner radius : a − g(x)
inner radius: |a| + f (x)
width : f (y) − g(y)
width : f (y) − g(y)
These are only a few cases for horizontal axis of rotation. If the axis of rotation is the x-axis use the y = a ≤ 0
case with a = 0. For vertical axis of rotation (x = a > 0 and x = a ≤ 0) interchange x and y to get appropriate formulas.
Work : If a force of F (x) moves an object in
Z b
a ≤ x ≤ b, the work done is W =
F (x) dx
a
Average Function Value : The average value of
Z b
1
f (x) on a ≤ x ≤ b is favg =
f (x) dx
b−a a
© Paul Dawkins - https://tutorial.math.lamar.edu
Calculus Cheat Sheet
Arc Length & Surface Area : The three basic formulas are,
Z b
Z b
L=
ds
SA =
2πy ds (rotate about x-axis)
a
Z
b
2πx ds (rotate about y-axis)
SA =
a
a
where ds is dependent upon the form of the function being worked with as follows.
s
s 2
2
2
dy
dx
dy
ds = 1 +
dx if y = f (x), a ≤ x ≤ b ds =
+
dt if x = f (t), y = g(t), a ≤ t ≤ b
dx
dt
dt
s
s
2
2
dx
dr
2
ds = 1 +
dy if x = f (y), a ≤ y ≤ b
ds = r +
dθ if r = f (θ), a ≤ θ ≤ b
dy
dθ
With surface area you may have to substitute in for the x or y depending on your choice of ds to match the
differential in the ds. With parametric and polar you will always need to substitute.
Improper Integral
An improper integral is an integral with one or more infinite limits and/or discontinuous integrands. Integral
is called convergent if the limit exists and has a finite value and divergent if the limit doesn’t exist or has
infinite value.
Infinite Limit
Z ∞
Z t
1.
f (x) dx = lim
f (x) dx
t→∞ a
a
Z ∞
Z c
Z
3.
f (x) dx =
f (x) dx +
−∞
−∞
Z
b
b
Z
2.
f (x) dx = lim
t→ −∞
−∞
f (x) dx
t
∞
f (x) dx provided both integrals are convergent.
c
Discontinuous Integrand
Z b
Z
1. Discontinuity at a :
f (x) dx = lim
t→a+
a
Z
3. Discontinuity at a < c < b :
b
Z
f (x) dx
t
b
b
Z
f (x) dx = lim
t→b−
a
Z
f (x) dx =
a
2. Discontinuity at b :
c
Z
f (x) dx
a
b
f (x) dx provided both are convergent.
f (x) dx +
a
t
c
Comparison Test for Improper Integrals : If f (x) ≥ g(x) ≥ 0 on [a, ∞) then,
Z ∞
Z ∞
1. If
f (x) dx is convergent then
g(x) dx is convergent (if larger converges so does the smaller).
Za∞
Z ∞a
2. If
g(x) dx is divergent then
f (x) dx is divergent (if smaller diverges so does the larger).
a
a
Z ∞
1
Useful fact : If a > 0 then
dx converges if p > 1 and diverges for p ≤ 1.
p
x
a
Approximating Definite Integrals
Z
b
For given integral
f (x) dx and n (must be even for Simpson’s Rule) define ∆x =
a
b−a
and divide [a, b]
n
into n subintervals [x0 , x1 ], [x1 , x2 ], …, [xn−1 , xn ] with x0 = a and xn = b then,
Z b
h
i
Midpoint Rule :
f (x) dx ≈ ∆x f (x∗1 ) + f (x∗2 ) + · · · + f (x∗n ) , x∗i is midpoint [xi−1 , xi ]
a
Z
b
i
∆x h
f (x0 ) + 2f (x1 ) + 2f (x2 ) + · · · + 2f (xn−1 ) + f (xn )
2
a
Z b
i
∆x h
Simpson’s Rule :
f (x) dx ≈
f (x0 ) + 4f (x1 ) + 2f (x2 ) + · · · + 2f (xn−2 ) + 4f (xn−1 ) + f (xn )
3
a
Trapezoid Rule :
f (x) dx ≈
© Paul Dawkins - https://tutorial.math.lamar.edu