Suppose I want to evaluate an expression of the type with . Let and be functions of x and y, e.g. and . And I am able to show analytically that . Knowing that , I can now rewrite to the expression . With this I can now deduce that if .
However, I want to use a MATLAB script to approximate the exact value of the boundary of the circle/ellipse using a while loop that evaluates at a lower boundary a (where ) and b (where ), so that . However, I do not know how to make MATLAB rewrite my symbolic expression for as a function , so that I can substitute the boundaries a and b. I would be glad about suggestions on how to solve this type of problem.