# integrate

• Jun 4th 2008, 02:44 PM
integrate
could you plz help!

can you find in terms of n the 3 possible values of ∫ cos nx dx with limits π and π/2 ?

Thanks
• Jun 4th 2008, 02:57 PM
o_O
The integral should be easy enough. Just treat n as a constant and let u = nx. You should get:

$\int_{\frac{\pi}{2}}^{\pi} \cos (nx) \: dx = ... = \frac{1}{n} \left[\sin(n\pi) - \sin \left(\frac{n\pi}{2}\right) \right]$

Are you suppose to find any 3 values that your definite integral can have depending on the value of n? Pick n = an even number, n = an odd number, n = a fraction such as 1/2.
• Jun 4th 2008, 03:06 PM