对t求导：x=a(lntant/2+cost)

题目

对t求导：x=a(lntant/2+cost)
答案是x’=acos^2t/sint
是x=a(lntan(t/2)+cost)

答案

先不写a最后乘cost'=-sint[lntan(t/2)]'=[1/tan(t/2)]*[tan(t/2)]'=[1/tan(t/2)]*sec^2(t/2)*(t/2)'=(1/2)sec^2(t/2)/tan(t/2)=(1/2)[1/cos^2(t/2)]/[sin(t/2)/cos(t/2)]=1/[2sin(t/2)cos(t/2)]倍角公式=1/sint相加x...