Question

Find the function value of cos^2 (7pi/8)

Answer 1

`\cos^2\frac{7\pi}8=\frac12\left(1+\cos\frac{7\pi}4\right)`

`=\frac12+\frac12\cos\left(-\frac\pi4\right)`

`=\frac12+\frac12\cos\frac\pi4`

`=\frac12+\frac1{2\sqrt2}`

`=(\sqrt2+1)/(2\sqrt2)`

`=\frac{2+\sqrt2}4`