∫xsinxdx=-∫x dcosx =-x cosx +∫cosx dx= sinx -x cosx
∫xe^x dx= ∫x de^x =x e^x-∫e^x dx =(x-1)e^x
就是分部积分法的应用
∫ xsinx/cos³x dx
= ∫ xsec²xtanx dx
= ∫ xsecx dsecx
= (1/2)∫ x dsec²x
= (1/2)xsec²x - (1/2)∫ sec²x dx
= (1/2)xsec²x - (1/2)tanx + c
= (1/2)(xsec²x - tanx) + c
不定积分∫xsinxdx等于多少不定积分∫xsinxdx等于多少
