Planimetry ( plane geometry) - shapes on plane Point and line basic geometrical shapes A not belong to a ( ); but B belong to a ( ); Two different lines isn’t crossing each other( parallels || ), or crossing in only one point *parallels in plane geometry Line segment AB : Ray: *AB & AC are additional to each other Two line segments are equal if they have the same length : Angle Angle ( 0, ab, AOB ): Two angles are equal if they have an equal measure of angle(degree): Types of angles ab - acute angle ac - right angle ad - obtuse angle ae - straight angle * ab & ac - adjacent angles to each other Vertical angles: * ab & b1a1 - equal and vertical a & b - perpendicular lines because c = 90 º Bisector of angle: ac = cb and c is bisector of ab Parallel lines a || b when 1 = 2 (or 3 = 4) * 1+ 3=180 º & 2+ 4=180 º ** if two lines parallel to third, then these two lines parallel to each other also Triangle Three points which not in one line ...