A point in the polar coordinate system is denoted by two numbers in parentheses separated by a comma. The first number represents the radius r (distance from the origin) and an angle θ (the greek letter theta) relative to the origin. This is visualized with the interactive below:

The polar coordinate system usually measures angles using the unit radians. A full rotation in radians is equal to the geometric constant τ (tau) approximately equal to 6.283. One radian is equal to the amount of rotation required to travel the length of one radius along the circumference of the circle.