∫(0->x) tf(x^2-t^2)dt=-1/2∫(0->x) f(x^2-t^2)d(x^2-t^2)令x^2-t^2=u则当t=0时 u=x当t=x时 u=0∴原式=-1/2∫(x->0) f(u)du =1/2∫(0->x) f(u)du∴导数是 1/2*f(x)
