题目

∫（1+sinx ）/（sin3x +sinx ）d x 怎么求

提问时间：2021-01-28

答案

∫ (1 + sinx)/(sin3x + sinx) dx
= ∫ (1 + sinx)/[2sin(3x + x)/2 * cos(3x - x)/2]
= (1/2)∫ dx/(sin2xcosx) + (1/2)∫ sinx/(sin2xcosx) dx
= (1/2)∫ dx/(2sinxcos²x) + (1/2)∫ sinx/(2sinxcos²x) dx
= (1/4)∫ cscxsec²x dx + (1/4)∫ sec²x dx
= (1/4)∫ cscx(1 + tan²x) dx + (1/4)tanx
= (1/4)∫ cscx dx + (1/4)∫ secxtanx dx + (1/4)tanx
= (1/4)ln| cscx - cotx | + (1/4)(secx + tanx) + C