The Mathematics of Art and Graphic Design, A Tutorial

There are a number of algebraic relations and functions that can be used to describe a drawing. The most common are the line, the parabola and the circle. In drawing we often only use segments of a line, a parabola or a circle(an arc).

Lines are defined uniquely with their slope and y-intercept. If you were to plot the lines

On the right hand side of the bear's dress, there are four sets of lines. Each set of lines are approximately perpendicular to each other(90 degree angle). The slope of the line becomes steeper as you from the back of the dress towards the bear's leg. Conversely, the slope of each corresponding perpendicular line becomes less steep as the lines approach the bear's leg.