Question

13题怎么写

Answer 1

先求一阶导，都对t求导，然后相除，二阶导是一阶导对x求导，也是一阶导先对t求导再除以x对t求导

Answer 2

dx/dt=2t/(1+t²)
dy/dt=1-1/(1+t²)=t²/(1+t²)

∴ dy/dx=dy/dt÷dx/dt=t/2

∴ d²y/dx²=1/2·dt/dx
=1/2÷dx/dt
=(1+t²)/(4t)