The from a system is a two-dimensional coordinate system in which each point on a plane is determined by a from a reference direction. The reference point is called and the ray from the pole in the reference point and an reference direction is The radial coordinate is often denoted by r. The angle is often denoted by 0. An equation of the form r-5 represents a and an equation of the form 0-/6 represents a ray. In general, curves described by polar coordinates have special names. For instance, consider the Archimedean spiral which was discovered by in 287-212 BC. The equation of the Archimedean spiral is of the form r=a+be. In the following, we have the graph of r=1+20. The values of 0 run between , r increases. So both the radius and angle of the points increase. and As 0 40 20 (8 from 0 to 8 m) -40 40 Newton the polar axis polar coordinate zero decreases increases circle -20 point. Archimedes -20 -40 infinity distance 20 triangular square angle the pole