# Math Help - Compound Angle Formula (check if this is right)

1. ## Compound Angle Formula (check if this is right)

Use the compound forumla to express each of the following as a single trigonometric function.

cos x cos x - sin x sin x
Would this just be cos (a + b)?
=cos2x

and

sin 5a cos 2a + cos 5a sin 2a
This would be sin (a + b)?
=sin7a

Appreciate the help.

2. Originally Posted by peekay
Use the compound forumla to express each of the following as a single trigonometric function.

cos x cos x - sin x sin x
Would this just be cos (a + b)?
=cos2x

and

sin 5a cos 2a + cos 5a sin 2a
This would be sin (a + b)?
=sin7a

Appreciate the help.