Question
Prove cos4x = 8 cos^4x-8 cos^2x+1
Answers
MathMate
Use the double angle formula:
cos(2A)=cos²(A)-sin²(A)
=2cos²(A)-1.
You will need to apply the formula twice, the first time to reduce cos(4x) in terms of cos(2x). The second time will reduce to the expression above.
cos(2A)=cos²(A)-sin²(A)
=2cos²(A)-1.
You will need to apply the formula twice, the first time to reduce cos(4x) in terms of cos(2x). The second time will reduce to the expression above.