x=cos(t^2)
dx/dt = -2t.sin(t^2)
y=tcos(t^2) -∫(1->t^2) [cosu/(2√u) ] du
dy/dt
=cos(t^2) - 2t^2.sin(t^2) -2t [cos(t^2)/(2t) ]
=-2t^2.sin(t^2)
dy/dx = (dy/dt)/(dx/dt) = t
d/dt (dy/dt ) =1
d^2y/dx^2
=d/dt (dy/dt ) / (dx/dt)
=-1/[2t.sin(t^2)]