解答
∫(sin(x))5(cos(x))51dx
解答
6ln∣sin(x)∣−23csc2(x)−41csc4(x)−3ln∣sin(x)+1∣+16(sin(x)+1)13+16(sin(x)+1)21−3ln∣sin(x)−1∣−16(sin(x)−1)13+16(sin(x)−1)21+C
求解步骤
∫(sin(x))5(cos(x))51dx
化简=∫sin5(x)cos5(x)1dx
使用换元积分法
=∫u5(1−u2)31du
将u5(1−u2)31用部份分式展开:u6+u33+u51−u+13−16(u+1)213−8(u+1)31−u−13+16(u−1)213−8(u−1)31
=∫u6+u33+u51−u+13−16(u+1)213−8(u+1)31−u−13+16(u−1)213−8(u−1)31du
使用积分加法定则: ∫f(x)±g(x)dx=∫f(x)dx±∫g(x)dx=∫u6du+∫u33du+∫u51du−∫u+13du−∫16(u+1)213du−∫8(u+1)31du−∫u−13du+∫16(u−1)213du−∫8(u−1)31du
∫u6du=6ln∣u∣
∫u33du=−2u23
∫u51du=−4u41
∫u+13du=3ln∣u+1∣
∫16(u+1)213du=−16(u+1)13
∫8(u+1)31du=−16(u+1)21
∫u−13du=3ln∣u−1∣
∫16(u−1)213du=−16(u−1)13
∫8(u−1)31du=−16(u−1)21
=6ln∣u∣−2u23−4u41−3ln∣u+1∣−(−16(u+1)13)−(−16(u+1)21)−3ln∣u−1∣−16(u−1)13−(−16(u−1)21)
u=sin(x)代回=6ln∣sin(x)∣−2sin2(x)3−4sin4(x)1−3ln∣sin(x)+1∣−(−16(sin(x)+1)13)−(−16(sin(x)+1)21)−3ln∣sin(x)−1∣−16(sin(x)−1)13−(−16(sin(x)−1)21)
化简 6ln∣sin(x)∣−2sin2(x)3−4sin4(x)1−3ln∣sin(x)+1∣−(−16(sin(x)+1)13)−(−16(sin(x)+1)21)−3ln∣sin(x)−1∣−16(sin(x)−1)13−(−16(sin(x)−1)21):6ln∣sin(x)∣−23csc2(x)−41csc4(x)−3ln∣sin(x)+1∣+16(sin(x)+1)13+16(sin(x)+1)21−3ln∣sin(x)−1∣−16(sin(x)−1)13+16(sin(x)−1)21
=6ln∣sin(x)∣−23csc2(x)−41csc4(x)−3ln∣sin(x)+1∣+16(sin(x)+1)13+16(sin(x)+1)21−3ln∣sin(x)−1∣−16(sin(x)−1)13+16(sin(x)−1)21
解答补常数=6ln∣sin(x)∣−23csc2(x)−41csc4(x)−3ln∣sin(x)+1∣+16(sin(x)+1)13+16(sin(x)+1)21−3ln∣sin(x)−1∣−16(sin(x)−1)13+16(sin(x)−1)21+C