单项选择题
A.-cosx+c B.cosx+c C.1/2(sin2x/2-x)+c D.1/2(2sin2x-x)+c
A.cosx+1/2cos2x+c B.cos2x-1/2cos4x+c C.x+(1/2)x2+c D.x-(1/2)x2+c
A.-1/x B.-(1/x2) C.1/x D.1/x2