Expressing following in one equation

Question

I have 3 variables: theta (optimal launch angle), h (launch height), v0 (velocity at launch). h and v0 are independent from each other. How do I express theta in terms of h and v0, if I have following:

Answer 1

You can't.

Imagine you were able to get some expression of $\theta_{opt}(v_0,h)$ from these two equations. What's to prevent me from adding an arbitrary third equation, for some other fixed value of $v_0$ and/or $h$?