SOLUTION: Using techniques with sum and difference formulas, find any acceptable formula for cos 3(theta) You do not have to fully simplify your answer, but you must at least simplify identi

Question 981304: Using techniques with sum and difference formulas, find any acceptable formula for cos 3(theta) You do not have to fully simplify your answer, but you must at least simplify identities.
Someone please help me. Thank you.
Found 2 solutions by josgarithmetic, macston:
Answer by josgarithmetic(39617) (Show Source): You can put this solution on YOUR website!

Hard to know at what stage you are finished.

Continuing----

Using the Pythagorean Identity for ,

------Most interesting because looks simplest.
Answer by macston(5194) (Show Source): You can put this solution on YOUR website!
.
T=theta
.
cos3T = cos(2T+T)...cos(a+b)=cos(a)cos(b)-sin(a)sin(b)
.
cos3T = cos2TcosT-sin2TsinT...cos(2a)=cos^2(a)-sin^2(a) and sin(2a)=2sinTcosT
.
cos3T = cosT(cos^2T-sin^2T)-sinT(2sinTcosT)
.
cos3T = cos^3T-sin^2cosT-2sin^2TcosT
.
cos3T = cos^3T-3sin^2TcosT...sin^2(a)=1-cos^2(a)
.
cos3T = cos^3T-3(1-cos^2T)(cosT)
.
cos3T = cos^3T-3(cosT-cos^3T)
.
cos3T = cos^3T+3cos^3T-3cosT
.
cos3T = 4cos^3T-3cosT

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