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∫Dx/(1+sinx)

先求不定积分 ∫1/sinx dx =∫sinx/sin²xdx =-∫1/sin²xdcosx =-∫1/(1-cos²x)dcosx =∫1/(cosx+1)(cosx-1)dcosx =∫[1/(cosx-1)-1/(cosx+1)]/2dcosx =[∫1/(cosx-1)dcosx-∫1/(cosx+1)dcosx]/2 =[∫1/(cosx-1)d(cosx-1)-∫1/(cosx+1)d(cos...

∫ dx/sinx = ∫ cscxdx = ln|cscx-cotx| + C = lntan(x/2) + C p + √(1+p^2) = e^(x/a), √(1+p^2) = e^(x/a) - p 1 + p^2 = e^(2x/a) - 2pe^(x/a) + p^2 e^(2x/a) -1 = 2pe^(x/a) p = (1/2)[e^(x/a) - e^(-x/a)] = sinh(x/a)

u = tan(x/2)、dx = 2/(1 + u²) du、sinx = 2u/(1 + u²) ∫ 1/(3 + sinx) dx = ∫ 1/[3 + 2u/(1 + u²)] * 2/(1 + u²) du = ∫ (1 + u²)/[3(1 + u²) + 2u] * 2/(1 + u²) du = 2∫ 1/(3u² + 2u + 3) du = 2∫ ...

如图所示:

方法一: ∫[1/(1+sinx)]dx =2∫{1/[sin(x/2)+cos(x/2)]^2}d(x/2) =2∫{1/[tan(x/2)+1]}^2{1/[cos(x/2)]^2}d(x/2) =2∫{1/[tan(x/2)+1]}^2[tan(x/2)+1] =-2/[1+tan(x/2)]+C。 方法二: ∫[1/...

2+sinx=2sin(x/2)^2+2cos(x/2)^2+2sin(x/2)cos(x/2) dx/(2+sinx)=sec(x/2)^2dx/[2+2tan(x/2)^2+2tan(x/2)] =d(tan(x/2))/[1+tan(x/2)+tan(x/2)^2] 令u=tan(x/2) 原积分=∫du/(1+u+u^2) =∫d(u+1/2)/[3/4+(u+1/2)^2](用∫dx/(a^2+x^2)公式,取a=√3/...

这个是三角函数的不定积分,分母应先进性化简,计算步骤为: ∫1/(sinx+cosx)dx =∫dx/√2sin(x+π/4) =-(√2/2)∫dcos(x+π/4)/sin^2(x+π/4) =-(√2/4){∫dcos(x+π/4)/[1-cos(x+π/4)]+∫dcos(x+π/4)/[1+cos(x+π/4)]} =-(√2/4)ln{[1+cos(x+π/4)]/[1-cos...

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