Looking at things from a fresh Angle.
 Radians vs Degrees
 We are all comfortable that a circle can be divided into $360^\circ$
 But we also know that the c++ trig functions want radians.
 What is a radian?
 wikipedia reference
 This is the SI unit for measuring an angle.
 It is a dimensionless unit,
 An angle is measured between 0 and $2\pi$ radians.
 Converting:
 $2\pi $ radians = $360^\circ$
 or $\frac{2\pi}{360^\circ}$
 which simplifies to $\frac{\pi}{180^\circ}$
 So
 $45^\circ = 45^\circ \times \frac{\pi}{180^\circ} $
 $ = \frac{45\pi}{180}radians $
 $ = \frac{\pi}{4}radians $
 Remember
Math.PI
is a constant in javascript.
 We need this because all trig functions take radians.
 But I don't know trig functions.
 Ok, but well....
 The functions cos and sin are used to compute the relationship between various angels of a right triangle.
 Given a right triangle (or a triangle with a $90^\circ$ angle.
 (Wikipedia)
 The nice part is that this gives us an easy way to go around a circle.
 (Wikipedia)
 $\cos(\theta) = \frac{adjacent}{hypotenuse}$
 $\sin(\theta) = \frac{opposite}{hypotenuse}$
 $\tan(\theta) = \frac{adjacent}{opposite}$
 sin and cos are great functions
 (Wikipedia again)

Math.cos(), Math.sin(), ...
all exist in javascript.
 These are the basis for Polar Coordinates
 The is an alternative way to describe a plane.
 Alternative to Cartesian.
 r is a distance from the origin
 $\Theta$ is an angle from the "x" axis.
 $x = r\cos(\Theta))$
 $y = r\sin(\Theta))$
 A demo
 Problem: Draw a 5 sided star centered on the canvas.
 Note that all of the points on a star are on a circle.
 Draw a star on the board.
 And that they are evenly spaced out.
 Can we find these points?
 Well the first is at 0 radians
 The others should be spaced out at $\frac{\pi}{5}$ radians.
 This is a take on a larger problem, A n/m star polygon
 n is the number of points (5)
 m is the skip factor between points (2)
 A 5/1 star polygon is the pentagon
 A 5/2 star polygon is the star.
 A 6/2 or 6/3 is problematic
 Look here