How do I do this trig. integral?

  • Thread starter Thread starter shreddinglicks
  • Start date Start date
  • Tags Tags
    Integral Trig
Click For Summary

Homework Help Overview

The discussion revolves around the integral ∫cos(x)^5 / sqrt(sin(x))dx, which falls under the subject area of trigonometric integrals. Participants are exploring various approaches to simplify or solve the integral without arriving at a definitive solution.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss breaking down cos(x)^5 and using trigonometric identities. There are attempts to express the integral in different forms, including using a substitution method with u = sin(x). Some participants question how to handle the identity and the remaining terms after substitution.

Discussion Status

The discussion is ongoing, with participants sharing their attempts and reasoning. There is a recognition of the challenges in applying the substitution effectively, and some guidance has been offered regarding the relationship between the variables involved. However, no consensus or resolution has been reached yet.

Contextual Notes

Participants are navigating the complexities of the integral and the implications of the trigonometric identities involved. There is an acknowledgment of the need to manage the terms resulting from the substitution, which may not be fully resolved in the current discussion.

shreddinglicks
Messages
225
Reaction score
7

Homework Statement


∫cos(x)^5 / sqrt(sin(x))dx


Homework Equations


∫cos(x)^5 / sqrt(sin(x))dx


The Attempt at a Solution



i tried to break up cos(x)^5

∫(cos(x)^2)(cos(x)^3)dx

I tried an identity

(1-sin(x)^2)(sin(x)^-.5)cosx^3

I tried to distribute the sin(x)^.5 and use a u sub but that's where I get stuck.
 
Physics news on Phys.org
Write the integral as:

##\int \frac{cos^4(x)cos(x)}{\sqrt{sin(x)}} dx##
##= \int \frac{(1-sin^2(x))^2cos(x)}{\sqrt{sin(x)}} dx##

##u = sin(x).. du = ..##
 
Zondrina said:
Write the integral as:

##\int \frac{cos^4(x)cos(x)}{\sqrt{sin(x)}} dx##
##= \int \frac{(1-sin^2(x))^2cos(x)}{\sqrt{sin(x)}} dx##

##u = sin(x).. du = ..##

I see, and du = cos(x)

that takes care of my cos(x) in the numerator but it doesn't take care of the identity.
 
shreddinglicks said:
I see, and du = cos(x)

that takes care of my cos(x) in the numerator but it doesn't take care of the identity.

Of course it does. If ##u = sin(x)## then ##u^2 = sin^2(x)##.
 

Similar threads

  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 15 ·
Replies
15
Views
2K
Replies
3
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 6 ·
Replies
6
Views
1K
  • · Replies 11 ·
Replies
11
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 9 ·
Replies
9
Views
2K