# The...er...derivendicular

Calculus Level pending

In this problem, two functions are defined to be perpendicular at all x in their domain if for every x in their domain, the tangent lines of those functions at x are perpendicular.

A function $$f(x)$$ defined on $$x \leq 0$$, is perpendicular at all x in their domain to the function $$f'(x)$$.

If $$f(0) = 0$$, what is $$f(-4.5)$$)?

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