Abstract: In tracing a functional equation, a maximum value of the functional equation and an intersection with another functional equation can be recognized on a graph of the functional equation. Coordinate values of any traced dot may include an intersection point discriminated to be a true intersection point or not. An intersection point between dots to be traced, can be traced with the trace interval changed to be finer than the display interval. The tracing cursor indicates specific points by a change in a color and/or shape of the cursor. A point intersection between different functions is determined on the basis of a difference value between traced values of respective functions.