逃出大城市
春芽
共回答了24个问题采纳率:91.7% 举报
1.令x=tant 则 cost=1/√(1+x^2)
原式=∫sect/tant*(sect)^2 dt
=∫sint/(cost)^4 dt
=-∫dcost/(cost)^4
=3/(cost)^3
=3/[√(1+x^2)]^3
2.令x=0.6sint (以下积分限均为0~π/2)
原式=∫0.36(sint)^2/(3cost)*0.6cost dt
=0.072*∫(sint)^2 dt
=0.072*π/4=9π/500
1年前
3