∫dx/(x√(a^2-x^2))

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∫dx/(x√(a^2-x^2))∫dx/(x√(a^2-x^2))∫dx/(x√(a^2-x^2))令x=a*sint(t在0到pi/2之间)则dx=a*cost*dt√(a^2-x^2)=√{a^

∫dx/(x√(a^2-x^2))
∫dx/(x√(a^2-x^2))

∫dx/(x√(a^2-x^2))
令x=a*sint(t在0到pi/2之间)
则dx=a*cost*dt
√(a^2-x^2)=√{a^2[1-(sint)^2]}=a*cost
原式=∫ a*cost*dt/(a*sint*a*cost)
=∫ dt/(a*sint)
=1/a*∫ sint*dt/(sint)^2
= -1/a*∫ d(cost)/[1-(cost)^2]
= -1/a*∫ d(cost)*[1/(1-cos)t+1/(1+cost)]/2
= -1/(2a)*[-ln(1-cost)+ln(1+cost)]
= -1/(2a)*ln[(1+cost)/(1-cost)]
而x=a*sint,sint=x/a,cost=√(1-x^2/a^2)
将cost代入,再化简即可