MATH 131-503 Fall 2015
2.1
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Chapter 2 Limits and Derivatives
2.1 The Tangent and Velocity Problems
The Tangent Problem
A tangent line to a curve is a line that touches the curve. In other words, a tangent line should
have the same direction as the curve at the point of contact.
A secant line is a line that cuts (intersects) a curve more than once.
We say that the slope of the tangent line is the limit of the slopes of the secants lines.
Example 1: (p. 90) Find an equation of the tangent line to the parabola y = x2 at the point
P (1, 1).
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MATH 131-503 Fall 2015
2.1
c
Wen
Liu
The Velocity Problem
average velocity=
change in position
time elapsed
The instantaneous velocity at t0 is defined to be the limiting value of these average velocities over
shorter and shorter time periods that starts at t0 .
Example 2: (p. 92) Suppose that a ball is dropped from the upper observation deck of the
CN Tower in Toronto, 450 m above the ground. Assume that the distance fallen after t seconds is
s(t) = 4.9t2 .
(a) Find the average velocity for the time period beginning when t = 5 and lasting 0.1 seconds.
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MATH 131-503 Fall 2015
2.1
c
Wen
Liu
(b) Find the average velocity for the time period beginning when t = 5 and lasting 0.05 seconds.
(c) Find the average velocity for the time period beginning when t = 5 and lasting 0.01 seconds.
(d) Estimate the instantaneous velocity of the ball after 5 seconds.
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