PieGraph::CalcSlice PHP Method

    protected function CalcSlice($angle_start, $angle_end, &$x_start, &$y_start, &$x_end, &$y_end)
    {
        $x_start = $this->radius_x * cos($angle_start);
        $y_start = ($this->reverse ? -1 : 1) * ($this->radius_y * sin($angle_start));
        $x_end = $this->radius_x * cos($angle_end);
        $y_end = ($this->reverse ? -1 : 1) * ($this->radius_y * sin($angle_end));
        $x_start += $this->x_centre;
        $y_start += $this->y_centre;
        $x_end += $this->x_centre;
        $y_end += $this->y_centre;
    }