College of Engineering, Architecture and Technology Name: ______________________________________ Course & Year: ______________ Module 1 Course Title Course Number Course Description : Integration Concepts : Integral Calculus : Math 122 : The course introduces the concepts of integration and its application to some physical problems such as evaluation of areas, volumes of revolution, force and work. The fundamental formulas and various techniques of integration are taken up and applied to both single variable and multi-variable functions. The course also includes tracing of functions of two variables for a better appreciation of the interpretation of the double and triple integral as volume of a three-dimensional region bounded by two or more surfaces Total Learning Time : 4 units (4 hours lecture per week) Pre-requisites : Differential Calculus (if there’s any) Overview: Integration is the process of finding for the antiderivative or the inverse of the derivative of a function. This chapter will discuss indefinite integrals, its definition and properties. This chapter will also discuss the different integral formulas for algebraic and transcendental functions. Learning Outcomes: At the end of this module, the student should be able to: 1. Demonstrate integration process of algebraic and transcendental functions. 2. Develop mastery on the use of formulas in integrating algebraic and transcendental functions 3. Evaluate Integrals. Indicative Content: This module discusses at least the following topics: The Indefinite Integral, Properties of Indefinite Integral, The Power Formula, Logarithmic Formula, Exponential Formula, Trigonometric Functions, Method by Trigonometric Transformations, Inverse Trigonometric Functions and Hyperbolic Functions. ENGR. SHAINA D. SUCGANG 1 College of Engineering, Architecture and Technology Name: ____________________________________ Course & Year: _____________________________ Date Submitted: __________ Rating: __________ Pre-Assessment: Evaluate the following integrals. 1. ∫(π₯ 3 − 6)ππ₯ 2. ∫ 3. ∫ ππ¦ √π¦ 5ππ§ π§5 4. ∫ (π − π₯)3 ππ₯ 2 5. ∫ (π‘ 3 + π‘) ππ‘ √ ENGR. SHAINA D. SUCGANG 2 Discussion: Anti-differentiation Anti-differentiation or integration is the reverse process to differentiation. For example, if π(π₯) = 2π₯, we know that this is the derivative of π(π₯) = π₯ 2 . If we shift the parabola π(π₯) = π₯ 2 by sliding it up or down vertically, all the points on the curve will still have the same tangent slopes, i.e. derivatives. For example: All have the same derivative function, π¦ ′ = 2π₯, so a general expression for this family of curves would be; π¦ = π₯2 + π where c is an arbitrary constant (called the integration constant). Note: Where possible, check your answer by differentiating, remembering that the derivative of a constant c, is zero. In mathematical notation, this anti-derivative is written as ∫ 2π₯ ππ₯ = π₯ 2 + π The integration symbol “∫ ” is an extended S for “summation”. (You will see why in Mathematics IM.) The “ππ₯” part indicates that the integration is with respect to π₯. For instance, the integral ∫ 2π₯ ππ‘ cannot be found, unless π₯ can be rewritten as some function of π‘. Indefinite Integrals We have been concerned principally with finding the derivative and differential of a given function. Suppose the process is reversed, i.e., the derivative or differential of a function is given, and we are asked to find the function. Such a function is called an integral ENGR. SHAINA D. SUCGANG 3 of the given derivative or differential. The process of finding it is called integration. The given function is called the integrand. Let f ο¨x ο© be a given function which is the derivative of a function F ο¨x ο© . We can express their relation by the equation F ο¨x ο© ο½ ο² f ο¨x ο©dx , Which is read “ F ο¨x ο© is equal to the integral of f ο¨x ο©dx ”. The symbol ο² is called the integral sign. The equation indicates that we must find a function F ο¨x ο© whose differential is f ο¨x ο©dx or whose derivative is f ο¨x ο© . As an example, if dy ο½ 5 x 4 dx, The following are possible solutions: y ο½ x 5 , y ο½ x 5 ο« 1, y ο½ x 5 ο 6, y ο½ x 5 ο« C, where C is any constant. The last solution is the general function whose differential is 5 x 4 dx . It embraces all the other solutions. This fact is written ο² 5x dx ο½ x 4 5 ο« C. Theorem: If F ο¨x ο© is a function whose differential is f ο¨x ο©dx , or whose derivative is f ο¨x ο© then F ο¨x ο© ο« C is a whole class of functions having the same differential (or derivative). General Properties of Indefinite Integrals The following are properties of indefinite integrals. I. ο² dv ο½ v ο« C II. III. ο² ο¨dv ο« dw ο« ... ο« dz ο© ο½ ο² dv ο« ο² dw ο« ... ο« ο² dz ο½ v ο« w ο« ... ο« z ο« C ο² cdv ο½ c ο² dv ο« C ο½ cv ο« C The Power Formula Let us derive and illustrate the first four formulas of integration. d ο¨v ο« C ο© ο½ dv , hence, we have the formula I. ο² dv ο½ v ο« C d ο¨v ο« w ο« ... ο« z ο« C ο© ο½ dv ο« dw ο« ... ο« dz, Thus, we have the formula ENGR. SHAINA D. SUCGANG 4 II. ο² ο¨dv ο« dw ο« ... ο« dz ο© ο½ ο² dv ο« ο² dw ο« ... ο« ο² dz ο½ v ο« w ο« ... ο« z ο« C . d ο¨cv ο« C ο© ο½ cdv, Where c and C are constants and v is a function of a variable, hence, we have the formula III. ο² cdv ο½ c ο² dv ο½ cv ο« C ο¦ v nο«1 οΆ d ο§ο§ ο« C ο·ο· ο½ v n dv, where n and C are constants, v is a function of a variable, and ο¨ n ο«1 οΈ is not equal to -1, hence, we obtain the formula v nο«1 n v dv ο½ ο«C IV. n οΉ ο1 ο² n ο«1 Formula IV is called the power formula for integration. Simple Trigonometric Functions Consider the differentials d ο¨ο cos v ο« C ο© ο½ sin v dv d ο¨sin v ο« C ο© ο½ cos v dv d ο¨tan v ο« C ο© ο½ sec 2 v dv d ο¨ο cot v ο« C ο© ο½ csc 2 v dv d ο¨sec v ο« C ο© ο½ sec v tan v dv d ο¨ο csc v ο« C ο© ο½ csc v cot v dv From the above differentials, the following integration formulas are verified. V. VI. VII. VIII. IX. X. ο² sin v dv ο½ ο cos v ο« C ο² cos v dv ο½ sin v ο« C ο² sec v dv ο½ tan v ο« C ο² csc v dv ο½ ο cot v ο« C ο² sec v tan v dv ο½ sec v ο« C ο² csc v cot v dv ο½ ο csc v ο« C 2 2 ENGR. SHAINA D. SUCGANG 5 Let us consider the following cases: I. Odd Powers of Sine and Cosine Let ∫ π πππ π’ πππ π π’ ππ’, where either of the two powers π or π is a positive odd integer or both of the two powers π and π are positive odd integers. Let π be a positive odd integer and in the form ∫ π πππ π’ πππ π−1 π’ cos π’ ππ’ and putting, πππ 2 π’ = 1 − π ππ2 π’ The process continues and a basic power formula is used to evaluate the integral. A similar process works for an odd power of sine using, π ππ2 π’ = 1 − πππ 2 π’ II. Even Powers of Sine and Cosine Let ∫ π πππ π’ πππ π π’ ππ’, where both of the two powers π and π are positive even integers. When both of the two powers are positive even integers, use the following identities. 1 π ππ2 π’ = 2 (1 − cos 2π’) 1 πππ 2 π’ = 2 (1 + cos 2π’) 1 sin π’ cos π’ = 2 sin 2π’ III. Powers of Tangent and Cotangent Let ∫ π‘πππ π’ ππ’ ππ πππ‘ π π’ ππ’, where, π is either an odd or an even integer. Put, π‘ππ2 π’ = π ππ 2 π’ − 1 πππ‘ 2 π’ = ππ π 2 π’ − 1 IV. Powers of Secant and Cosecant Let ∫ π ππ π π’ ππ’ ππ ππ π π π’ ππ’, where, π is an even integer. Put, π ππ 2 π’ = 1 + π‘ππ2 π’ ππ π 2 π’ = 1 + πππ‘ 2 π’ ENGR. SHAINA D. SUCGANG 6 V. Products of Tangent and Secant and Cotangent and Cosecant Let ∫ π‘πππ π’ π ππ π π’ ππ’ and ∫ πππ‘ π π’ ππ π π π’ ππ’, where, π is either an odd or an even integer and π is an even integer. Put, π ππ 2 π’ = 1 + π‘ππ2 π’ ππ π 2 π’ = 1 + πππ‘ 2 π’ VI. Products of Sine and Cosine For the product of sine and cosine of different angles, use the following ∫ sin(ππ’) cos(ππ’) ππ’ = ∫ sin(ππ’) sin(ππ’) ππ’ = ∫ cos(ππ’) cos(ππ’) ππ’ = cos(π−π)π’ 2(π−π) sin(π−π)π’ 2(π−π) − cos(π−π)π’ 2(π−π) − cos(π+π)π’ 2(π+π) sin(π+π)π’ + 2(π+π) +πΆ cos(π+π)π’ 2(π+π) +πΆ +πΆ Logarithmic Function Consider the differential dv d ο¨ln v ο« C ο© ο½ v Therefore, we have dv XI. ο² v ο½ ln v ο« C ππ’ The logarithmic formula is, ∫ π’ = ln u + c, u > 0 The integral of any quotient when the numerator is the derivative of the denominator is equal to the logarithm of the numerator. Exponential Function Consider the differential d e v ο« C ο½ e v dv , and ο¨ ο© ο¦ av οΆ d ο§ο§ ο« C ο·ο· ο½ a v dv ο¨ ln a οΈ Thus, v v XII. ο² e dv ο½ e ο« C , and ENGR. SHAINA D. SUCGANG 7 VI’ av ο² a dv ο½ ln a ο« C v Inverse Trigonometric Functions Let us consider the differential, v dv ο¦ οΆ d ο§ arcsin ο« C ο· ο½ , and 2 a ο¨ οΈ a ο v2 v dv ο¦1 οΆ d ο§ arctan ο« C ο· ο½ 2 2 a ο¨a οΈ a ο«v Thus, dv v XIII. ο² ο½ arcsin ο« C a a2 ο v2 dv 1 v XIV. ο² 2 ο½ arctan ο« C 2 a a a ο«v Hyperbolic Functions I. II. III. IV. V. VI. VII. VIII. ο² sec h v dv ο½ tanh v ο« C ο² cosh v dv ο½ sinh v ο« C ο² sinh v dv ο½ cosh v ο« C ο² csc h v dv ο½ ο coth v ο« C ο² tanh v dv ο½ ln cosh v ο« C ο² sec h v tanh v dv ο½ ο sec h v ο« C ο² coth v dv ο½ ln sinh v ο« C ο² csc h v cot h v dv ο½ ο csc h v ο« C 2 2 Constant of Integration All of integrations include the constant of integration, C. Any pure constant always disappears during the differentiation because the differential of a constant is zero. The constant of integration may assume any constant value, and in order to fix its value, more conditions must be given. Suppose we wish to find a function whose differential is 3x 2 ο 4 x ο« 6 dx , and which shall have a value 10 when x=1. ο¨ Solution: ο© T get the function, integrate the differential, 2 3 2 ο² ο¨3x ο 4 x ο« 6ο©dx ο½ x ο 2 x ο« 6 x ο« C ENGR. SHAINA D. SUCGANG 8 From the given conditions, this result is 10 when x=1. Thus, 10 ο½ 1 ο 2 ο« 6 ο« C : C ο½5 Therefore the required function is x 3 ο 2 x 2 ο« 6 x ο« 5. The geometric meaning of the constant of integration may be understood from the following problem: Find the equation of the curve whose slope at any point is twice its abscissa at said point. dy Solution: The slope at any curve at any point is given by . Thus, dx dy ο½ 2 x or dy ο½ 2 xdx . By means of integration, dx 2 ο² dy ο½ 2ο² xdx or y ο½ x ο« C Since C may assume any value, this equation only represents the family of parabolas opening upwards, with vertices on the y-axis. If for example, the parabola passes thru the point ο¨2,1ο© , then y=1 when x=2. Thus, 1 ο½ 4 ο« C : C ο½ ο3 Therefore, the required equation is y ο½ x 2 ο 3 . The physical meaning of the constant of integration may be interpreted from the following problem in motion. Derive the equations of motion of a particle moving in a straight vertical line under the influence of the acceleration of gravity “g”, which is constant. Solution: We have learned that dv dv a ο½ , or g ο½ . Thus, dt dt dv ο½ g dt or v ο½ gt ο« C To get the value of C, suppose when t=0 sec, v=2 ft per sec. Then, 2 ο½ 0ο«C : Cο½2 Therefore, v ο½ gt ο« 2 ds ds We also know that v ο½ , or gt ο« 2 ο½ . Thus, dt dt 1 2 ds ο½ ο¨gt ο« 2ο©dt or s ο½ gt ο« 2t ο« C 2 To get the value of C, suppose s=3 when t=0. Then, C ο½ 3 . The distance equation becomes 1 s ο½ gt 2 ο« 2t ο« 3 2 ENGR. SHAINA D. SUCGANG 9 Definite Integral After studying the fundamental formulas and other methods of integration, let us focus our attention to the physical applications of integration in solving various problems such as areas, volumes of solids, lengths of curves, centroids, moments of inertia, fluid pressure and work done by a variable force. For this purpose, we will employ definite integration using the definite integral. Assume a given function f ο¨x ο© to be continuous between x ο½ a and x ο½ b and let F ο¨x ο© be an anti-derivative or integral of f ο¨x ο© . When x ο½ a, F ο¨xο© ο½ F ο¨aο© and when x ο½ b, F ο¨xο© ο½ F ο¨bο©. The difference F ο¨bο© ο F ο¨a ο© or change in the value of F ο¨x ο© in the interval x ο½ a, x ο½ b is called the definite integral of f ο¨x ο© between the limits x ο½ a and x ο½ b , or simply the integral of f ο¨x ο© from a to b. b Definite integral will be denoted by the symbol ο² f ο¨x ο©dx where the numbers a and a b are called the lower and upper limits of integration, respectively. The value of the definite b integral is given by the equation ο² f ο¨x ο©dx ο½ οF ο¨x ο©οa ο½ F ο¨bο© ο F ο¨a ο© b a The above equation, can be stated as “the definite integral is the value of the indefinite integral at the upper limit minus its values at the lower limit.” Note: The definite integral is independent of C. The value of definite integral is not a function of the variable of integration but a Constant number. 1. 0 2 ο© x4 οΉ x ο« 2 x dx ο½ οͺ ο« x 2 οΊ ο½ 4 ο« 4 ο 0 ο½ 8 ο«4 ο»0 ο²ο¨ 2 ο© 3 ο° ο° ο° t 1 1 1 ο©ο° οΉ 1 2. ο² cos dt ο½ ο² 2 ο¨1 ο« cos t ο© dt ο½ οt ο« sin t ο02 ο½ οͺ ο« 1 ο 0οΊ ο½ ο¨ο° ο« 2ο© 0 2 2 2 2ο«2 ο» 4 0 2 2 2 3. Evaluate ο² x 3 ln x dx . 1 Solution: By means of integrating by parts. Let u ο½ ln x, dv ο½ x 3 dx dx 1 du ο½ , v ο½ x4 x 4 Therefore, ο² 2 1 2 ο©1 οΉ 1 2 x ln x dx ο½ οͺ x 4 ln xοΊ ο ο² x 3 dx ο«4 ο»1 4 1 3 ENGR. SHAINA D. SUCGANG 10 2 1 οΉ ο©1 ο½ οͺ x 4 ln x ο x 4 οΊ 16 ο»1 ο«4 1 1 ο½ ο¨16 ln 2 ο 0 ο© ο ο¨16 ο 1ο© 4 16 15 ο½ 4 ln 2 ο 16 Properties of the Definite Integral Certain properties of definite integrals are as follows: ο¨1ο© ο² f ο¨xο©dx ο½ οο² f ο¨xο©dx ο¨2ο© ο² f ο¨xο©dx ο½ ο² f ο¨xο©dx ο« ο² f ο¨xο©dx ο¨3ο© ο² f ο¨xο©dx ο½ ο² f ο¨t ο©dt ο½ ο² f ο¨z ο©dz b a a b c b b a b a d c f a c e Integrals of Even and Odd Function A function is called an even function if it remains unchanged when x is replaced by ο x . f ο¨ο x ο© ο½ f ο¨x ο© An odd function is one whose sign changes when x is replaced by ο x. f ο¨ο xο© ο½ ο f ο¨xο© In integrating an even or odd function, the following properties will be followed: Theorem I: If f ο¨x ο© is an even function, then ο² f ο¨x ο© dx ο½ 2ο² f ο¨x ο© dx a a οa a 0 Theorem II: If f ο¨x ο© is an odd function, then ο² f ο¨x ο©dx ο½ 0 οa Properties of the Definite Integral Certain properties of definite integrals are as follows: ο¨1ο© ο² f ο¨xο©dx ο½ οο² f ο¨xο©dx ο¨2ο© ο² f ο¨xο©dx ο½ ο² f ο¨xο©dx ο« ο² f ο¨xο©dx ο¨3ο© ο² f ο¨xο©dx ο½ ο² f ο¨t ο©dt ο½ ο² f ο¨z ο©dz b a a b c b b a b a d c f a c e ENGR. SHAINA D. SUCGANG 11 Integrals of Even and Odd Functions A function is called an even function if it remains unchanged when x is replaced by ο x . f ο¨ο x ο© ο½ f ο¨x ο© An odd function is one whose sign changes when x is replaced by ο x. f ο¨ο xο© ο½ ο f ο¨xο© In integrating an even or odd function, the following properties will be followed: Theorem I: If f ο¨x ο© is an even function, then ο² f ο¨x ο© dx ο½ 2ο² f ο¨x ο© dx Theorem II: If f ο¨x ο© is an odd function, the a a οa a 0 ο² f ο¨xο©dx ο½ 0 οa Wallis’ Formula: Consider the integral ο² ο° 2 0 sin m x cos n x dx 2οΉ ο© 2οΉ ο© ο¨ ο©ο¨ ο© ο¨ ο©ο¨ ο© m ο 1 m ο 3 ..... or n ο 1 n ο 3 ...... or οͺ οΊ οͺ ο° 1ο» ο« 1οΊο» ο« m n 2 This will yield into ο² sin x cos x dx ο½ ο¨ο‘ ο© 0 2οΉ ο© οͺο¨m ο« n ο©ο¨m ο« n ο 2ο©......or 1οΊ ο« ο» Where m and n are integers ο³ 0. ο‘ο½ ο° , If m and n are both even, 2 ο‘ ο½ 1, If either one or both are odd, And that the lower and upper limits are 0 and ο° respectively. 2 The above expression is called Wallis’ Formula. ENGR. SHAINA D. SUCGANG 12 Exercises/Drills: 1. 1 If π¦ ′ = π₯, then π¦ = 2 π₯ 2 + π Solution: 1 (Check: π¦ ′ = 2 β 2π₯ + 0 = π₯ ) οΌ 1 If π¦ ′ = π₯ 2 , then π¦ = 3 π₯ 3 + π 2. Solution: 1 οΌ (Check: π¦ ′ = 3 β 3π₯ 2 + 0 = π₯ 2 ) 3.∫ π₯ 4 ππ₯ = π₯5 5 +πΆ Solution: = π₯5 +πΆ 5 4. ο² ο¨4 x 4 ο« 3 x ο« 5ο©dx = 4ο² x 4 dx ο« 3ο² xdx ο« 5ο² dx Solution: 4 x 5 3x 2 = ο« ο« 5x ο« C 5 2 5. ο² ο¨x 2 ο© 2 ο« 2 dx Solution: ο¨ ο© ο½ ο² x 4 ο« 4 x 2 ο« 4 dx = ο² x 4 dx ο« 4ο² x 2 dx ο« 4ο² dx x5 4x3 ο« ο« 4x ο« C = 5 3 ENGR. SHAINA D. SUCGANG 13 ο² ο¨x 6. ο© 3 ο 5 xdx 2 Solution: Let v ο½ x 2 ο 5 dv ο½ d x 2 ο 5 ο½ 2xdx ο¨ ο© We introduce 2 after the integral sign, and neutralize it by putting its reciprocal before the integral sign. Hence, ο¨x = 7. 2 ο² ο¨x 2 ο© ο¨ ο© 3 3 ο¦1οΆ ο 5 xdx ο½ ο§ ο· ο² x 2 ο 5 ο¨2 ο©xdx ο¨2οΈ ο 5ο© ο«C 8 4 . ο² sin ο± cosο± dο± Solution: Let v ο½ sin ο± dv ο½ d ο¨sin ο± ο© ο½ cosο± dο± Then, ο² sin ο± cos ο± dο± ο½ ο¨ο ο©ο² cosο± ο¨ο sin ο± ο©dο± = 8. ο cos 2 ο± ο«C 2 Evaluate ο² sin 4 x dx Solution: Let v ο½ 4x dv ο½ 4dx Insert 4 after the integral sign and 1 before the integral sign. Thus 4 ο¦1οΆ ο² sin 4 x dx ο½ ο§ο¨ 4 ο·οΈο² sin 4 x ο¨4ο©dx 1 = ο cos 4 x ο« C 4 ENGR. SHAINA D. SUCGANG 14 1 2 9. Evaluate x ο² cos 3dx Solution: x 1 , dv ο½ dx 3 3 x xο¦1οΆ ο² cos 3 dx ο½ ο¨3ο©ο² cos 3 ο§ο¨ 3 ο·οΈ dx x = 3 sin ο« C 3 Let v ο½ 10. Evaluate ο² x sec 2 3x 2 dx Solution: Let v ο½ 3x 2 , dv ο½ 6 x 1 2 2 2 2 ο² x sec 3x dx ο½ 6 ο² 6 x sec 3x dx 1 = tan 3 x 2 ο« C 6 11. 1 Evaluate ο² csc 2 ln x dx x Solution: Let v ο½ ln x, dv ο½ 1 ο² x csc 12. 2 dx x ln x dx ο½ ο cot ln x ο« C Evaluate ο² e 2 x sec e 2 x tan e 2 x ο¨2 ο©e 2 x dx Solution: Let v ο½ e 2 x , dv ο½ 2e 2 x dx 1 2x 2x 2x 2x 2x ο² e sec e dx ο½ 2 ο² sec tan e ο¨2ο©e dx 1 = sec e 2 x ο« C 2 ENGR. SHAINA D. SUCGANG 15 13. Evaluate ο² sin 2 x cos 3 x dx . Solution: cos 3 x ο½ cos 2 x cos x = 1 ο sin 2 x cos x ο¨ ο© Thus, ο² sin 2 ο¨ ο© x cos 3 x dx ο½ ο² sin 2 x 1 ο sin 2 x cos x dx = ο² sin 2 x cos x dx ο ο² sin 4 x cos x dx sin 3 x sin 5 x ο ο«C 3 5 Evaluate ο² sin 2 ο± cos 2 ο± dx = 14. Solution: = ο² ο¨sin ο± cos ο± ο© dο± 2 ο¦1 οΆ = ο² ο§ sin 2ο± ο·dο± ο¨2 οΈ 2 ο¦1οΆ = ο² ο§ ο· sin 2 2ο± dο± ο¨2οΈ 1 = ο² ο¨1 ο cos 4ο± ο© dο± 8 1 1 = ο² dο± ο ο² cos 4ο± dο± 8 8 1 1 = ο± ο sin 4ο± ο« C 8 32 15. Evaluate ο² sin 4 ο± dο± Solution: = ο² ο¨sin 2 ο± ο© dο± 2 =ο² 1 ο¨1 ο cos 2ο± ο©2 dο± 4 ο¨ ο© 1 1 ο 2 cos 2ο± ο« cos 2 2ο± dο± ο² 4 1 ο¦ 1 1 οΆ = ο² ο§1 ο 2 cos 2ο± ο« ο« cos 4ο± ο· dο± 4 ο¨ 2 2 οΈ = ENGR. SHAINA D. SUCGANG 16 3 1 1 = ο± ο sin 2ο± ο« sin 4ο± ο« C 8 4 32 16. Evaluate ο² cot 3 x dx Solution: = ο² cot x cot 2 x dx = ο² cot x ο¨csc 2 x ο©dx = ο² cot x csc 2 x dx ο ο² cot x dx =ο 17. cot 2 x ο ln sin x ο« C 2 Evaluate ο² sec 4 x tan 4 x dx Solution: = ο² tan 4 x sec 2 x sec 2 x dx = ο² tan 4 xο¨tan 2 x ο« 1ο©sec 2 x dx = ο² tan 6 x sec 2 x dx ο« ο² tan 4 x sec 2 x dx = 18. tan 7 x tan 5 x ο« ο«C 7 5 Evaluate ο² sec 5 x tan 3 x dx Solution: = ο² sec 4 x tan 2 x sec x tan x dx = ο² sec 6 x sec x tan x dx ο ο² sec 4 x sec x tan x dx = sec 7 x sec 5 x ο ο«C 7 5 ENGR. SHAINA D. SUCGANG 17 ο² ο¨x 2 19. Evaluate 3 ο« 2 x ο©dx 0 Solution: 2 ο© x4 οΉ ο½ οͺ ο« x2 οΊ ο«4 ο»0 ο½ 4ο« 4ο0 ο½8 ο° 2 20. t Evaluate ο² cos 2 dt 2 0 Solution: ο° 1 2 ο¨1 ο« cos t ο© dt 2 ο²0 ο° 1 ο½ οt ο« sin t ο02 2 1 ο©ο° οΉ 1 ο½ οͺ ο« 1 ο 0οΊ ο½ ο¨ο° ο« 2 ο© 2ο«2 ο» 4 ο½ 21. 2 Evaluate ο² x 3 ln x dx . 1 Solution: By means of integrating by parts. Let: u ο½ ln x, dv ο½ x 3 dx dx 1 du ο½ , v ο½ x4 x 4 Therefore, ο² 2 1 2 ο©1 οΉ 1 2 x ln x dx ο½ οͺ x 4 ln xοΊ ο ο² x 3 dx ο«4 ο»1 4 1 3 2 1 οΉ ο©1 ο½ οͺ x 4 ln x ο x 4 οΊ 16 ο»1 ο«4 1 1 ο½ ο¨16 ln 2 ο 0 ο© ο ο¨16 ο 1ο© 4 16 15 ο½ 4 ln 2 ο 16 ENGR. SHAINA D. SUCGANG 18 22. Evaluate 16 ο² 1 ο« x dx 0 Solution: Using Algebraic Substitution, Let 1 ο« x ο½ z, x ο½ z ο1 x ο½ ο¨z ο 1ο© , dx ο½ 2ο¨z ο 1ο© dz Changing the limits, If x ο½ 0, z ο½1 If x ο½ 16, z ο½ 5 Therefore, 2 16 ο² 0 1 1 ο« x dx ο½ 2ο² z 2 ο¨z ο 1ο© dz 5 1 5 ο©2 5 2 3 οΉ 2οͺ z 2 ο z 2 οΊ ο½ 34.33 3 ο»1 ο«5 3 23. Evaluate ο² a 0 2 2 ο¦ 23 οΆ ο§ a ο x 3 ο· dx ο§ ο· ο¨ οΈ Solution: Using Trigonometric Substitution, Let 1 3 1 3 x ο½ a sin ο± x ο½ a sin 3 ο± dx ο½ 3a sin 2 ο± cosο± dο± Changing the limits, If x ο½ 0, sin ο± ο½ 0, or ο± ο½ 0 If x ο½ a, sin ο± ο½ 1, or ο± ο½ 3 Therefore, ο² a 0 ο° 2 3 2 2 2 ο° ο¦ 23 οΆ ο¦ 2 οΆ2 ο§ a ο x 3 ο· dx ο½ ο² 2 ο§ a 3 ο a 3 sin 2 ο± ο· 3a sin 2 ο± cosο± dο± ο§ ο· ο· 0 ο§ ο¨ οΈ ο¨ οΈ ο½ 3a 2 ο² ο° 2 0 cos 4 ο± sin 2 ο± dο± ENGR. SHAINA D. SUCGANG 19 ο½ 3a 2 2 ο° 1 ο² ο¨1 ο« cos 2ο± ο© 4 sin 2 0 2 2ο± dο± ο° ο° οΉ 3 ο© ο½ a 2 οͺο² 2 sin 2 2ο± dο± ο« ο² 2 sin 2 2ο± cos 2ο± dο± οΊ 0 8 ο«0 ο» ο° 3 ο©1 ο½ a 2 οͺ ο² 2 ο¨1 ο cos 4ο± ο©dο± ο« 8 ο«2 0 ο² ο° 2 0 οΉ sin 2 2ο± cos 2ο± dο± οΊ ο» ο° 3 ο©1 1 1 οΉ2 ο½ a 2 οͺ ο± ο sin 4ο± ο« sin 3 2ο± οΊ 8 ο«2 8 6 ο»0 3 2 ο© 1 ο¦ ο° οΆ οΉ 3ο°a 2 ο½ a οͺ ο§ ο· ο 0οΊ ο½ 8 ο«2 ο¨ 2 οΈ ο» 32 24. Evaluate ο² ο° sin 4 x cos 6 x dx 2 0 Solution: By Wallis’ formula, m and n are both even. ο² Therefore, 25. Evaluate ο° sin 4 x cos 6 x dx ο½ 2 0 ο² οο¨3ο©ο¨1ο©ο¨5ο©ο¨3ο©ο¨1ο©ο ο¦ ο° οΆ ο½ 3ο° ο§ ο· οο¨10ο©ο¨8ο©ο¨6ο©ο¨4ο©ο¨2ο©ο ο¨ 2 οΈ 512 ο° 2 0 cos 3 x sin 6 x dx Solution: Since m is odd Therefore, 26. ο² ο° 2 0 cos 3 x sin 6 x dx ο½ Evaluate ο² ο¨2ο©ο¨5ο©ο¨3ο©ο¨1ο© ο¨1ο© ο½ 2 ο¨9ο©ο¨7ο©ο¨5ο©ο¨3ο©ο¨1ο© 63 ο° 2 0 sin 6 x cos x dx Solution: ο² ο° 2 0 sin 6 x cos x dx ο½ ο¨5.3.1ο©ο¨1ο© ο¨1ο© ο½ 1 7.5.3.1 ENGR. SHAINA D. SUCGANG 7 20 27. Evaluate ο² ο° 2 0 cos 8 x dx Solution: ο² ο° 2 0 cos 8 x dx ο½ ο¨7.5.3.1ο©ο¨1ο© ο¦ ο° οΆ ο½ 35ο° ο§ ο· 8.6.4.2 ο¨ 2 οΈ ENGR. SHAINA D. SUCGANG 256 21 College of Engineering, Architecture and Technology Name: ____________________________________ Course & Year: _____________________________ Date Submitted: __________ Rating: __________ Evaluation: Evaluate the following integrals and check by differentiation. Write your solutions on the space provided. 1. ο² 5 xdx 2. ο² ο¨x ο 3ο© dx 4 ENGR. SHAINA D. SUCGANG 3. ο² ο¨5 ο x ο©dx 4. ο² ο¨a ο« bx ο©dx . 2 22 ο² ο¨8 x 5. 6. ο² sin ο© 4 ο 5 x 2 ο« 2 dx 7. ο² cos 3 4 x dx 8. ο² sin ENGR. SHAINA D. SUCGANG 3 2 4 x dx ο± dο± . 23 9. ο² cos 2 1 ο± dο± 3 10. ο² sin 5 3 x dx ENGR. SHAINA D. SUCGANG 4dx 11. ο² 3x ο« 2 12. ο² 1 ο 5x 2dx 24 13. ο²x xdx 2 ο4 14. ο²x 2 15. ο¨2 x ο« 3ο©dx ο²x 2 ο« 3x ο« 1 ο¨x ο 1ο©dx ο 2 x ο« 16 ENGR. SHAINA D. SUCGANG 25 Evaluate Problems 1-10 by algebraic substitution. 1. ο² a 2. ο² 4 dx 0 2ο« x 3. 0 ο°2 4 0 ο² x 3 a 2 ο x 2 dx cos x dx ENGR. SHAINA D. SUCGANG 26 4. a ο² ο¨y 0 y 3 dy 2 ο a2 ο© x2 ο a2 dx x 5. ο² 2a 6. ο² 4 x dx 0 2ο« x a 2 ENGR. SHAINA D. SUCGANG 27 7. 8. 9. 4 dx 2 x x2 ο1 ο² a x 3 dx x2 ο« a2 ο² ο¨ 0 ο² 4 0 ln ο¨ ο¦ a2 οΆ ο§ο§ Put x ο½ ο· v ο·οΈ ο¨ ο© ο© z ο« 2 dz ENGR. SHAINA D. SUCGANG 28 10. ο² 2a a a2 ο« x2 dx x4 Solve problems 11-18 by trigonometric substitution. 11. Prob. 1 12. Prob. 5 ENGR. SHAINA D. SUCGANG 29 13. Prob. 6 14. Prob. 7 15. Prob. 8 ENGR. SHAINA D. SUCGANG 30 Additional Reading: Calculus Differential and Integral by Ignacio J. Sevilla, Carlos G. Cruz, Eduardo Calayan, Demtrio A. Quirino Jr., Jose M. Mijares References: H.J. Terano. (2015). A Simplified Text in Differential Calculus. Camarines Sur Plytechnic Colleges ENGR. SHAINA D. SUCGANG 31