MathGrapher: Online Graphic Calculator

"Free online 2D graphing calculator (plotter), or curve calculator, that can plot piecewise, linear, quadratic, cubic, quartic, polynomial, trigonometric, hyperbolic, exponential, logarithmic, inverse functions given in different forms: explicit, implicit, polar and parametric. It can also graph arbitrary inequalities or system of inequalities, slope fields (vector fields or direction fields), visualize Riemann Sum. Plots can be styled and customized according to needs." (thx to Paul)