1/8 cos 4a + sin^2a × cos^2 - 0.375 упростить

1/8(cos²2a-sin²2a)+1/4*4sin²a*cos²a-0,375==1/8cos²2a-1/8sin²2a+1/4sin²2a-0,375==1/8cos²2a+1/8sin²2a-0,375==1/8(cos²2a+sin²2a)-0,375==0,125*1-0,375=-0,25