# Math Help - sin and cosine function

1. ## sin and cosine function

Please need help with this question!

2. ## Re: sin and cosine function

Use $(a+b)^2 = a^2+2ab+b^2$.

3. ## Re: sin and cosine function

I tried doing this and i ended up with 2sin(a)cos(a)=0 where a=alpha, but i am not too sure where to go from there?

4. ## Re: sin and cosine function

Calmo
Study trigonometry a little bit. you have to know that 2sinacosa=sin(2a)
therefore you have to solve the equation sin(2a)=0 which is very easy...

5. ## Re: sin and cosine function

OK
2 sin A cos A = 0 that is when sinA = 0 or cos A = 0
sin A = 0 when A = 0 or pi and cos A = 0 when A = pi/2
I am sure you can finish it now