# How do you use the product to sum formulas to write #sin(x+y)cos(x-y)# as a sum or difference?

##### 1 Answer

Feb 14, 2017

#### Explanation:

As

=

=

Now as

=

=

=

=

- as
#cos(-A)=cosA#

=

- as
#cos(pi/2-A)=sinA# and#cos(pi/2+A)=-sinA#