Question

三角函数代换法求不定积分中 含根号x方-a方时,

Answer 1

因为(sect)'=sect*tant

所以dx=asect*tantdt

推导

(sect)'=(1/cost)'

=[1'*cost-1*(cost)']/(cost)²

=[0+sint]/(cost)²

=(sint/cost)*(1/cost)

=sect*tant