question: public PlaPointFloat change_size ( double p_new_size ) { if ( v_x == 0 && v_y == 0 ) { return this ; } double length = Math . sqrt ( v_x * v_x + v_y * v_y ) ; double new_x = ( v_x * p_new_size ) / length ; double new_y = ( v_y * p_new_size ) / length ; return new PlaPointFloat ( new_x , new_y ) ; }
target:  Approximates a FloatPoint on the line from zero to this point with distance p_new_length from zero.