第1个回答 2012-03-11
解 :
y=sin^4(x/4)+cos^4(x/4)
=4sin^3(x/4)*[sin(x/4)]'+4cos^3(x/4)*[cos(x/4)]'
=4sin^3(x/4)*cos(x/4)*(x/4)'-4cos^3(x/4)*sin(x/4)*(x/4)'
=sin^3(x/4)cos(x/4)-cos^3(x/4)sin(x/4)
=sin(x/4)cos(x/4)*[sin²(x/4)-cos²(x/4)]
=(1/2)sin(x/2)*[-cos(x/2)]
=(1/4)sinx本回答被网友采纳