Help with Washer Method Integration

[festx]

I am having a problem with this particular problem:

 

Integrate pi(sin(x)^2 - (1/2)^2) from pi/4 to pi/2

 

I used a trig identity and got this:

 

pi [ (x/2 - sin(2x)/4) - (1x/4) ]

 

however when I evaluate this from pi/4 to pi/2 I am not

getting the correct result.

 

Any help is much appreciated.

 

steve

[Dave]

I get the answer as being pi*(pi+4)/16, which I think is right.

[festx]

Yes it is. I was making a mistake with the integration and did not catch it until yesterday.

 

Thanks for yor help.

[Dave]

Not a problem

[Guest Luis]

I need help too for the washer method

 

washer method

 

y=x, y=0, y=4, x=6

[Dave]

It would help if you gave us the integral you're trying to evaluate