Question

Помогите по тригонометрии.. √50 cos^2 11п8-√50 sin^2 11п8

Answer 1

$displaystyle sqrt{50}*cos^2frac{11pi }{8}-sqrt{50}*sin^2frac{11pi}{8}=sqrt{50}(cos^2frac{11pi}{8}-sin^2frac{11pi }{8})=\\=sqrt{50}*cos frac{2*11pi }{8}=sqrt{50}*cosfrac{11pi}{4}=sqrt{50}*cos(2pi+frac{3pi}{4})=\\= sqrt{50}*cosfrac{3pi}{4}=sqrt{50}*frac{-sqrt{2} }{2}= -5$