The complex numberis represented by the vector (arrow) from the origin to the point. Its length is r and its angle with the right side of the x-axis is q. We draw a perpendicular (in green) from the point to the x-axis: That makes a right triangle and we can use the Pythagorean theorem: And since we know that , So the trigonometric form of is or Or if yout teacher wants you to use radians, then . Edwin