`dy/dx = (dy/dt)/(dx/dt) = (1/t)/(2t) = 1/(2t^2) `

`(d^2y)/(dx^2) = d/dx(dy/dx) = d/dt(dy/dx) dt/dx `

`= -1/2 t^{-3} (1/(2t)) = -1/(4t^4)`

This is always positive, so the function is concave upward for all t where its second derivative is defined, which is to say all `t ne 0` .