Question

обчисліть 6 cos^2 Pi/8 - 3 =

Answer 1

$6* cos^{2} frac{ pi }{8} -3=3*(2* cos^{2} frac{ pi }{8} -1 )=3*cos(2* frac{ pi }{8} )=3*cos frac{ pi }{4} =$
$=3* frac{ sqrt{2} }{2} = frac{3 sqrt{2} }{2}=1,5* sqrt{2}$