- #1
ilikephysics
- 18
- 0
Express the sines and cosines in exponential form and integrate to show that (integral from -pi to pi) sin(3x)cos(4x)dx=0
What I'm thinking is that I should use sin x=e^x-e^-x/2 and cos x=e^x+e^-x/2. And I should multiply sin times 3 and cos times 4 and integrate. And get something like this:
(e^3pi+e^-3pi/2 * e^4pi-e^-4pi/2) - (e^-3pi+e^3pi/2 * e^-4pi-e^4pi/2)=0
I don't think this is right though. Can someone help please?
What I'm thinking is that I should use sin x=e^x-e^-x/2 and cos x=e^x+e^-x/2. And I should multiply sin times 3 and cos times 4 and integrate. And get something like this:
(e^3pi+e^-3pi/2 * e^4pi-e^-4pi/2) - (e^-3pi+e^3pi/2 * e^-4pi-e^4pi/2)=0
I don't think this is right though. Can someone help please?