求不定积分∫1/(1+sinx)dx
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令 x=2t,则 dx = 2dt,sinx = sin(2t) = 2 sint cost
∫ dx / (1 + sinx)
= ∫ 2dt / (sin²t + cos²t + 2 sint cost)
= ∫ 2dt / (sin t + cos t)²
= ∫ 2dt / [√2 sin (t + π/4) ]²
= ∫ csc² (t + π/4) dt
= - ctg (t + π/4) + C
= - ctg (x/2 + π/碧喊肆4) + C
结渗旁果的其他表达方式悔轿:
tan(x/2 - π/4) + C
2 / [1 + ctg(x/2)] + C
∫ dx / (1 + sinx)
= ∫ 2dt / (sin²t + cos²t + 2 sint cost)
= ∫ 2dt / (sin t + cos t)²
= ∫ 2dt / [√2 sin (t + π/4) ]²
= ∫ csc² (t + π/4) dt
= - ctg (t + π/4) + C
= - ctg (x/2 + π/碧喊肆4) + C
结渗旁果的其他表达方式悔轿:
tan(x/2 - π/4) + C
2 / [1 + ctg(x/2)] + C
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