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积分xcscx^2dx

题目详情
积分xcscx^2dx
▼优质解答
答案和解析
分部积分法
∫x(cscx)^2dx=∫x/(sinx)^2dx=∫xd(-cotx)= - xcotx+∫cotx/dx = -xcotx+∫1/sinxd(sinx) = -xcotx+ln|sinx|+C
∫xcsc(x^2)dx=1/2*∫1/sin(x^2)d(x^2)=1/2∫1/sintdt=1/2∫sint/(sint)^2dt
=-1/2∫1/(1-(cost)^2)d(cost)=-1/4(∫[1/(1-cost)+1/(1+cost)]d(cost))
=-1/4*[ln(1+cost)-ln(1-cost)]+C
= -1/4ln[(1+cos(x^2))/(1-cos(x^2))]+C