1. ## simplify the experession

use the addition and subtraction formulas to simplify the experession

sin(x+y)sin(x-y)
write the answer in terms of sin x and cos y only

2. Originally Posted by cm3pyro
use the addition and subtraction formulas to simplify the experession

sin(x+y)sin(x-y)
write the answer in terms of sin x and cos y only
$sin(a+b)=sin(a)cos(b)+sin(b)cos(a)$ and $sin(a-b)=sin(a)cos(b)-sin(b)cos(a)$...now apply that

3. i did ..but i am coming up with the worng answer.

4. Originally Posted by cm3pyro
i did ..but i am coming up with the worng answer.
well since I am sure you know that $a^2-b^2=(a+b)(a-b)$ we have that case here...except in reverse...so it should be $sin(a)^2cos(b)^2-sin(b)^2cos(a)^2$