x=tant
sint/cost=x
sin^2t=x^2cos^2t
sin^2t=x^2*(1-sin^2t)
sin^2t=x^2-x^2sin^2t
(x^2+1)sin^2t=x^2
sin^2t=x^2/(x^2+1)
sint=x/√(x^2+1)
微积分 不定函数 第二类换元法的题目 最后一步看不懂
x=tant
sint/cost=x
sin^2t=x^2cos^2t
sin^2t=x^2*(1-sin^2t)
sin^2t=x^2-x^2sin^2t
(x^2+1)sin^2t=x^2
sin^2t=x^2/(x^2+1)
sint=x/√(x^2+1)