function isPtInsideSector(r, a, rBnds, aBnds) {
    if(!isAngleInsideSector(a, aBnds)) return false;

    var r0, r1;

    if(rBnds[0] < rBnds[1]) {
        r0 = rBnds[0];
        r1 = rBnds[1];
    } else {
        r0 = rBnds[1];
        r1 = rBnds[0];
    }

    return r >= r0 && r <= r1;
}
is pt (r,a) inside sector?

@param {number} r : pt's radial coordinate
@param {number} a : pt's angular coordinate in *radians*
@param {2-item array} rBnds : sector's radial bounds
@param {2-item array} aBnds : sector's angular bounds in *radians*
@return {boolean}