求不定積分∫(x²;-9)^1/2/xdx

求不定積分∫(x²;-9)^1/2/xdx

令x = 3secθ,dx = 3secθtanθdθ,√(x²;- 9)=√(9sec²;θ- 9)= 3tanθ,x > 3
∫√(x²;- 9)/x dx
=∫√(9sec²;θ- 9)/(3secθ)·(3secθtanθdθ)
=∫3tanθ·tanθdθ
= 3∫sec²;θ- 1 dθ
= 3tanθ- 3θ+ C
= 3·√(x²;- 9)/3 - 3arcsec(x/3)+ C
=√(x²;- 9)- 3arccos(3/x)+ C