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).

You could do the division and write this as (Math.PI/3), but this is unwise. The Java compiler does the division when it compiles the bytecode. So the executing program does not waste time or space doing it. But your program has lost clarity if you do it.

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

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