Expert: Paul Klarreich - 3/18/2009

Question
2(cos^2)3a-1. how would you simplify the given expression? I know that you
need to use the trig formulas just i don't know how to get the answers.

Answer
Questioner:   melie
Country:  United States
Category:  Advanced Math
Private:  No
 
Subject:  hw help
Question:  2(cos^2)3a-1. how would you simplify the given expression? I know that you need to use the trig formulas just i don't know how to get the answers.
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Write it correctly:

2 cos^2(3a) - 1.

Now find a formula in:

http://en.wikipedia.org/wiki/List_of_trigonometric_identities

that matches it perfectly.

Then you will match the 3a with the argument: (Hint: it's a double-angle formula.)

And you will have it.  Next step: MEMORIZE the formulas, and you will go right away to the right one.  Did your teacher forget to tell you: Trig takes work.  Lazy people need not apply.