I need help with trigonometric identities, I'm really confused with this questions.
Derive this identity from the sum and difference formulas for cosine:
sin a sin b = (1 / 2)[cos(a – b) – cos(a + b)]
I need the claculation and reason.

Question

I need help with trigonometric identities, I'm really confused with this questions.
Derive this identity from the sum and difference formulas for cosine:
sin a sin b = (1 / 2)[cos(a – b) – cos(a + b)]
I need the claculation and reason.

ganeshie8 · Answer

Question says :   `Derive this identity from the sum and difference formulas for cosine`

ganeshie8 · Answer

do u remember the sum/difference formulas for cosine ?

anonymous · Answer

Do u know that
cos(a - b) = cos(a)cos(b) + sin(a)sin(b) 
cos(a + b) = cos(a)cos(b) - sin(a)sin(b)

anonymous · Answer

@ShantelT1

anonymous · Answer

No sorry I don't really understand this.

anonymous · Answer

These are the sum/difference formulas for cosine.
The first formula is the sum and the second one is difference.
You just learn them for now.

anonymous · Answer

Now u have to just subtract the second equation from the first,and u will get what u need....