Question

7 sqrt 2 cos^2*5п/8 - 7 sqrt 2 sin^2*5п/8 помогите решить плс времени мало

Answer 1

$7sqrt{2 cos^{2} frac{5pi}{8/}}-7 sqrt{2}=7 sqrt{2 frac{1+cos frac{10pi}{8}}{2}-7 sqrt{2}$
$7sqrt{1+cos frac{5pi}{4}}-7 sqrt{2}$
$7sqrt{1- frac{ sqrt{2}}{2} }-7 sqrt{2}$