tutorial for HTML canvas's arc function

I can not figure out what all the parameters to the arc() function are (by experimentation) and I have not found any tutorial that seems to explain them. Where would a good explanation of the arc() function be?

From stackoverflow

• According to MDC:

  arc(x, y, radius, startAngle, endAngle, anticlockwise)
  

  x, y, and radius are obviously circle parameters. startAngle and endAngle are in radians, starting east. anticlockwise is a boolean.

  Sparr : your link is missing a :

  strager : Thanks. Link has been corrected.

• arc(x, y, radius, startAngle, endAngle, anticlockwise)
  

  The first three parameters, x and y and radius, describe a circle, the arc drawn will be part of that circle. startAngle and endAngle are where along the circle to start and stop drawing. 0 is east, Math.PI/2 is south, Math.PI is west, and Math.PI*3/2 is north. If anticlockwise is 1 then the direction of the arc, along with the Angles for north and south, are reversed.

  https://developer.mozilla.org/En/Canvas_tutorial/Drawing_shapes