# In Leibniz notation, how do you write the second derivative of y with respect to the square of x?

I know how to write in Leibniz notation for more plain-vanilla expressions like the the second derivative of y with respect to x. But I am not sure how to write, in Leibniz notation, the second derivative of y with respect to expressions more complex than a single variable. In, for example, the second derivative of y with respect to the square of x, would I just use parentheses and write $$dy^2/d(x^2)^2$$?

• It’s $d^2y$, not $dy^2$. – KM101 Jan 7 '19 at 18:50

Indeed, if $$z=x^2$$ and you need $$\frac{d^2y}{dz^2} = \frac{d^2 y}{d\left(x^2\right)^2}$$