How to Solve Trigonometric Integrals with Odd Powers?

In summary, the integral of cos[x]*(sin[x])^5dx can be solved using the method for odd powers, where u=\sin xdx and the resulting integral is -u+2u^3-u^5.
  • #1
physstudent1
270
1

Homework Statement


The integral of cos[x]*(sin[x])^5dx


Homework Equations





The Attempt at a Solution



I split it into cos[x]*(sin[x])^2 * (sin[x])^2 * sin[x]

then each sin^2[x] term becomes (1-cos[x]^2)

so you end up with the integral of cos[x]*(1-cos[x]^2)^2*sin[x]dx

let u=cos[x]
-du=sin[x]dx

so it comes to the integral of -u*(1-u^2)^2 which foils out to be

-u+2u^3-u^5 then integrating this gives

-(1/2)u^2 +(2/4)*u^4 - (1/6)*u^6+c

replacing all u's with cos[x] of course at the end I just want to make sure this is correct because I have to hand it in tomarrow and this is the first of these problems I have tried and I don't want to do them all wrong.
 
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  • #2
[tex]\int\cos x \sin^{5}xdx[/tex]

Yes?

Let [tex]u=\sin xdx[/tex] and it's solved.
 
  • #3
I'm sorry I wasn't clear enough in the explanation you must use "the method for odd powers to evaluate the integral" since we are just learning this technique.
 
  • #4
physstudent1 said:
I'm sorry I wasn't clear enough in the explanation you must use "the method for odd powers to evaluate the integral" since we are just learning this technique.
Well then your answer is correct!
 

FAQ: How to Solve Trigonometric Integrals with Odd Powers?

What are trigonometric integrals?

Trigonometric integrals are integrals that involve trigonometric functions such as sine, cosine, and tangent. They can be solved using various trigonometric identities and techniques.

Why are trigonometric integrals important?

Trigonometric integrals are important in many areas of science and mathematics, including physics, engineering, and statistics. They are used to solve various problems involving periodic functions and can also be used to find the area under a curve.

What are some common trigonometric identities used in solving integrals?

Some common trigonometric identities used in solving integrals include the Pythagorean identities, double angle identities, and half angle identities. These identities can help simplify the integral and make it easier to solve.

What are the basic steps for solving a trigonometric integral?

The basic steps for solving a trigonometric integral include simplifying the integral using trigonometric identities, making a substitution to change the form of the integral, and then using integration techniques such as integration by parts or trigonometric substitution.

What are some applications of trigonometric integrals in real life?

Trigonometric integrals have various applications in real life, such as calculating the displacement and velocity of an object in simple harmonic motion, finding the area of a sector in a circle, and determining the period and frequency of a wave. They are also used in engineering for designing and analyzing structures, and in physics for solving problems involving forces and motion.

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