Question

Use the half angle formula to find exact value of cos(3pi/8)

Answer 1

so it it says to use half angle formula...
We know
\[\cos^2(\frac{x}{2})=\frac{1}{2}(1+\cos(x))\]

Answer 2

\[\frac{3 \pi}{8}=\frac{x}{2}\]
What will you be pluggin in for x?