You are Here: Home >< Maths

# Integration and volumes watch

1. Question:

Problem: They have no substituted values into... They've only substituted values into the integral of cos^5 x
Why is this?

Also what is the need to let y = sint and make the expression in terms of y? Is it to get the "exact answer"?

Posted from TSR Mobile
2. (Original post by ps1265A)
Question:

Problem: They have no substituted values into... They've only substituted values into the integral of cos^5 x
Why is this?

Also what is the need to let y = sint and make the expression in terms of y? Is it to get the "exact answer"?

Posted from TSR Mobile
I can't follow what you're saying and your attachment isn't very clear either! I assume you're talking about the volume part of the question.

Do you have a standard formula for a volume integral when using parametric coordinates?

Do you agree with the integral that they write down in the first place?
3. Pi[Integral[(y^2)(dx/dT)dT] is what you are looking for in part b

Which ultimately comes down to the integral of sin^2(2t)•cos(t)dt in which I suggest you manipulate sin(2t)=2cos(t)sin(t) then use a substitution on the integral

### Related university courses

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: January 25, 2015
Today on TSR

### Exam Jam 2018

Join thousands of students this half term

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams