Доказать тождество 4cos^(4)alpha - 2cos2alpha - 1/2cos4alpha = 3/2

Question

Доказать тождество 4cos^(4)alpha - 2cos2alpha - 1/2cos4alpha = 3/2

Answer 1

4(1+сos2a)²/4-2cos2a-1/2*(2cos2a-1)=
=1+2cos2a+cos²2a-2cos2a-cos²2a+1/2=1 1/2=3/2
3/2=3/2