## LINES AND ANGLES- ESSENTIAL POINTS

• A line-segment has two end points.
• A ray has only one end point (its vertex).
• A line has no end points on either side.
• An angle is formed when two lines (or rays or line-segments) meet.
•  Pairs of Angles Condition Two complementary angles Measures add up to 90° Two supplementary angles Measures add up to 180° Two adjacent angles Have a common vertex and a common arm but no common interior. Linear pair Adjacent and supplementary

• When two lines a and b intersect; the point of their meet is called the point of intersection.
• When 2 lines do not meet at any point however far we extend them, we call these lines as parallel lines.
• Line: A line is perfectly straight and extends forever in both directions.
• Line segment: A line segment is the part of a line between two points.
• Ray: A ray is part of a line that starts at one point and extends forever in one direction.
• Intersecting lines: Two or more lines that have one point in common.
• Transversal: A line intersects two or more lines that lie in the same plane in distinct points.
• Parallel lines: Two lines on a plane that never meet. They are always the same distance apart.
• Complementary Angles: Two angles that add to 90°.
• Supplementary Angles: Two angles that add to 180°.
• Adjacent Angles: Two angles have a common vertex and a common arm but no common interior points.
• Linear pairs: A pair of adjacent angles whose non-common sides are opposite rays.
• Vertically Opposite Angles: Two angles formed by intersection of two lines that have common arm.
• Angles made by Transversal: When two lines are intersecting by a transversal, eight angles are formed.
• Transversal of Parallel Lines: If two parallel lines are intersected by a transversal, then each pair of:
• Corresponding angles are congruent.
• Alternate interior angles are congruent.
• Alternate exterior angles are congruent.
• If the transversal is perpendicular to the parallel lines, all of the angles formed are congruent to 90° angles.
• Sum of any 2 sides of triangle is greater than its third side.
• In right angled triangle, hypotenuse is the longest side.
• Sum of angles of triangle is 180 degree.
• A, B, C are collinear if AB + BC = AC.