Question

$sqrt{32} cos^{2} frac{ pi }{8} - sqrt{8}$

Answer 1

$sqrt{8}( sqrt{4}cos^{2} pi /8-1)= sqrt{8}(2cos ^{2} pi /8-1)= sqrt{8}(cos frac{2 pi }{8})=2 sqrt{2}cos frac{ pi }{4}=$$2 sqrt{2}* frac{ sqrt{2} }{2} =2$