Question

Вычислите: соs в степени 4 3пи/8 - sin в степени 4 3пи/8

Answer 1

 Cos⁴ 3π/8 - Sin⁴ 3π/8 = ( Cos² 3π/8 - Sin² 3π/8)( Cos² 3π/8 + Sin² 3π/8 )=
=( Cos² 3π/8 - Sin² 3π/8) * 1= ( Cos² 3π/8 - Sin² 3π/8)= Cos 3π/4 = -√2/2