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

cos^4x+sin^4x=1(1+cos2x)²/4+(1-cos2x)²/4=11+2cos2x+cos²x+1-2cos2x+cos²2x=42cos²x=2cos²x=0cosx=0x=π/2+πk,k∈z