Long description

The fighure shows a graph with two axes, labelled x-axis and y-axis, which intersect near the middle of the diagram, marked 0. An arrow is drawn from the origin at 0 into the upper right quadrant of the graph. The length of the arrow is labelled r and the angle it makes with the horizontal x-axis is labelled theta. A horizontal dashed line from the end of this arrow intersects the y-axis at a point marked y. A vertical dashed line from the end of this arrow intersects the x-axis at a point marked x.