Question

Enter the expression 2cos2(θ)−1, where θ is the lowercase Greek letter theta.

Answer 1

\[cos(2\theta)\]

Answer 2

wow thanks

Answer 3

It's my pleasure.

Answer 4

How would you get it though?

Answer 5

Sorry for the late reply.

Answer 6

\[2\cos^{2}\theta-1=2\cos^{2}\theta-(\sin^{2}\theta+\cos^{2}\theta)=\cos^{2}\theta-\sin^{2}\theta\]
\[=cos\theta cos\theta-sin\theta sin\theta=cos(\theta+\theta)=cos(2\theta)\]