令x'(t)=p,x''=dp/dt=dp/dx*dx/dt=pdp/dx方程化为pdp/dx+√(1-p^2)=0-pdp/√(1-p^2)=dx√(1-p^2)=x+Cp=±√(1-(x+C)^2)dx/±√(1-(x+C)^2)=dt±arcsin(x+C)=t+Dx=sin(±t+C1)+C2
