Zeros of a Function Calculator

This finds the real zeros of a function numerically rather than by algebra, so it is not limited to the shapes that have a formula. Type f(x) using x and the usual operators, with sin, cos, exp, ln, sqrt and the rest available, then give the range to search. It samples that range, closes in on every sign change by bisection and checks the dips that never cross, so a zero the curve merely touches is usually caught too. Only real zeros inside the range are reported, complex zeros are never found, and two zeros closer together than the sampling step can hide each other. For a quadratic or a cubic an exact solver will give you the roots in closed form instead.