Using basic identities to simplify cosx - cos^3x

[Jessika]

Using basic identities to simplify the expression.
How to simplify cosx-cos^3x

I know the answer is cos(x)sin^2(x)
But I just don't know how to get to there?

 

[wjm11]

Using basic identities to simplify the expression.
How to simplify cosx-cos^3x

I know the answer is cos(x)sin^2(x)
But I just don't know how to get to there?

Factor out a cosx and use one of the Pythagorean trig identities. They are easily looked up.