How do you use the double angle or half angle formulas to simplify #cos(2a) cos(a) - sin(2a) sin(a)#?
1 Answer
Sep 30, 2015
Simplify trig expression.
:
cos (2a).cos (a) - sin (2a).sin (a)
Explanation:
Use the trig identity: cos (a + b) = cos a.cos b - sin a.sin b
cos (2a).cos (a) - sin (2a).sin (a) = cos (2a + a) = cos 3a
