# Finding this antiderivative

• Feb 12th 2009, 02:31 PM
fattydq
Finding this antiderivative
10(sin(2x)/sin(x))

I have no idea how to tackle something like this, could someone help me out?
• Feb 12th 2009, 02:44 PM
Scott H
Remember that $\sin 2x = 2\sin x \cos x$.
• Feb 12th 2009, 03:05 PM
fattydq
What? 2sin(x) does not equal 2sin(x)cos(x)
• Feb 12th 2009, 03:07 PM
Chris L T521
Quote:

Originally Posted by fattydq
What? 2sin(x) does not equal 2sin(x)cos(x)

From trig, $\sin(2x)=2\sin x\cos x$

This is not the same as saying $2\sin x$.
• Feb 12th 2009, 03:21 PM
fattydq
Ok wow, am I just supposed to know that? It seems to me like Calc II is just getting out of hand, like there's all these things we're just expected to know already that I've never even heard of, and I got an A+ in calc I.
• Feb 12th 2009, 03:33 PM
GaloisTheory1
Quote:

Originally Posted by fattydq
Ok wow, am I just supposed to know that? It seems to me like Calc II is just getting out of hand, like there's all these things we're just expected to know already that I've never even heard of, and I got an A+ in calc I.

it's a trig identity...you should know more of them to become better with more problems. good luck in Calc II