Question

найдите значение выражения √2cos^2 3pi/8- √2sin^2 3pi/8

Answer 1

$sqrt2, cos^2frac{3pi }{8}-sqrt2, sin^2frac{3pi }{8}=sqrt2cdot (cos^2frac{3pi }{8}-sin^2frac{3pi }{8})=\\=sqrt2cdot cosfrac{6pi }{8}=sqrt2cdot cosfrac{3pi}{4}=sqrt2cdot (-frac{sqrt2}{2})=-1\\\star ; ; cos^2alpha -sin^2alpha =cos, 2alpha ; ; star$

Answer 2

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