Limiting angles of rotate_extrude in OpenSCAD 2015.3

rotate_splice.scad

intersection() {
    rotate_extrude() {
        translate([20, 0]) circle(5, $fn = 16);
    }
    translate([0, 0, -5]) linear_extrude(10) rotate_splice(5, 20, 50);
}

module rotate_splice(count, angle_length, radius) {
    for(i = [0:count - 1]) {
        angle_begin = 360 / count * i;
        angle_end = angle_begin + angle_length;
        slice = [
            [0, 0], 
            [radius * sin(angle_begin), radius * cos(angle_begin)],
            [radius * sin(angle_end), radius * cos(angle_end)]
        ];
        polygon(slice);
    }
}