# Math Help - Finding two integrals

1. ## Finding two integrals

Hello. I am having trouble with four problems from my homework.
I don't know why but the answers I get seem wrong and I am not quite sure what I am doing. (although happily i think I completed the rest with no problems yay! just these four are killing me!)
I also am in a situation where I can't spend too much time online so any help is appreciated!

I need to make a substitution and then evaluate the integral but i think i am doing the substitution part incorrectly.

and

thank you!

2. Originally Posted by curimath
Hello. I am having trouble with four problems from my homework.

I don't know why but the answers I get seem wrong and I am not quite sure what I am doing. (although happily i think I completed the rest with no problems yay! just these four are killing me!)
I also am in a situation where I can't spend too much time online so any help is appreciated!

I need to make a substitution and then evaluate the integral but i think i am doing the substitution part incorrectly.

and

thank you!
1) Substitute $u = \sqrt{x} \Rightarrow u^2 = x$ and you get a standard form.

2) Substitute $u = \sin x$ and the problem essentially reduces to finding $\int \cos^3 u \, du$ which you should know how to do.

3. thank you!

helped me a lot! :)