Question

Решите уравнение: cos^4x+cos^4(x-pi/2)=1

Answer 1

cos^4x+sin^4x=1
(1+cos2x)²/4+(1-cos2x)²/4=1
1+2cos2x+cos²x+1-2cos2x+cos²2x=4
2cos²x=2
cos²x=0
cosx=0
x=π/2+πk,k∈z