So I have 2 problems that I can't figure out. The first one:

sqrt(4-4sin^2(x))
[0,2pi/3]



First I factor out the 4 and take the 2 out making it:

2*Integral (1-sin^2(x))

Then I Change 1-sin^2(x) to cos^2(x) and take the square root to make it cosx.

2*Integral (cosx)

The integral is just sinx so it becomes 2sinx|[0,2pi/3]
Shouldn't the answer just be sqrt(3)?? It keeps telling me I'm wrong.
"Don't forget that sqrt(y^2) = |y|, not y (unless y is nonnegative)."




For the second problem I don't really know where to begin. Thanks for reading!

This post was edited by ChickenxChaser on Feb 21 2014 01:50pm

I didn't really read closely but I think that might be your problem right there.

Can x not be 2pi/3 for a sine function?

sure it can

sorry i looked at it closer, there is a tiny mistake in your logic....

(cos(x)^2)^(1/2) != cos(x)

Haha what does it equal then? I'm so confused lol

I believe it has to deal with:

"Don't forget that sqrt(y^2) = |y|, not y (unless y is nonnegative)."

i havent done much integration in years, so i am not too entirely sure on this.

This post was edited by cialda on Feb 21 2014 05:53pm

you'll need to integrate by 2 set of x's
or find trig id equivalent
or use trig sub

So it's because I didn't split it into abs(cosx) and do it for cosx and -cosx??

I believe that is your issue. You will have to adjust your bounds for when cos goes negative

ya,cosine=negative after pi/2

This post was edited by saber_x3 on Feb 21 2014 06:05pm