How do you simplify cos(α+β)cos(αβ)?

1 Answer
Dec 17, 2016

2sinαsinβ

Explanation:

Use the following formulas to solve this problem.

cos(A+B)=cosAcosBsinAsinB

cos(AB)=cosAcosB+sinAsinB

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

cos(α+β)cos(αβ)

=cosαcosβsinαsinβ(cosαcosβ+sinαsinβ)

=cosαcosβsinαsinβcosαcosβsinαsinβ

=2sinαsinβ

Hopefully this helps!