Two Pi radians.

Dividing a Circle

The Java trigonometric functions are static methods of the Math. They take radians for their arguments (as do such functions in most programming languages). Here is the complete method:

  private void drawStar( int x, int y, int size )
    int endX, endY ;
    // Six lines radiating from (x,y)
    for ( int i = 0; i<6; i++ )
      endX = x + (int)(size*Math.cos( (2*Math.PI/6)*i ));
      endY = y - (int)(size*Math.sin( (2*Math.PI/6)*i ));  // Note "-"
      graph.drawLine( x, y, endX, endY );

The circle is divided into six pieces. The constant pi is available in Java as Math.PI. There are two pi radians per circle. One sixth of a circle is (2*Math.PI/6).

The minus sign is used in the calculation of endY because y increases in value going down. Using a "+" would also work because of symmetry.


What does (int) do in the statement

endY = y - (int)(size*Math.sin( (2*Math.PI/6)*i ));