Question

cos^2 (п/8) - sin^2 (2п/8)

Answer 1

$cos^{2}frac{pi}{8}-sin^{2}frac{2pi}{8}=frac{1+cosfrac{pi}{4}}{2}-frac{1-cosfrac{pi}{2}}{2}=frac{cosfrac{pi}{4}}{2}=frac{sqrt{2}}{4}$