Graphmatica is an equation plotter which supports five types of planar graphs (including polar, parametric, logarithmic, inequalites and limited implicit plots), plots planar vector fields and solutions of the corresponding differential equations, unlimited graphs on screen at once, saving setup information and lists of equations, flexible grid labeling, lock-on coordinate cursor and several ways to resize the grid. Its calculus options include symbolic differentiation, drawing of tangent lines, and numerical integration (you use a mouse to select points and areas).