LINES AND ANGLES

LINES AND ANGLES

SOME IMPORTANT POINTS TO REMEMBER

·         If a ray stands on the line, then the sum of the two adjacent  angles so formed is 180° and vice versa. This property is called as the Linear pair axiom.

·         If two lines intersect each other, then the vertically opposite angles are equal.

·         If a transversal intersects two parallel lines , then

                              i.     each pair of corresponding angles is equal.

                             ii.     each pair of alternate interior angles is equal.

                           iii.     each pair of interior angles on the same side of the transversal is supplementary.

·         If a transversal intersects tow lines such that , either

                              i.     any one pair of corresponding angles is equal, or

                             ii.     any one pair of alternate interior angles is equal, or

                           iii.     any one pair of interior  angles on the same side of the transversal is supplementary , then the lines are parallel  l.

·         Lines which are parallel to a given line are parallel to each other.

·         The sum of the three angles of a triangle is 180°.

·         If a side of a triangle is produced , the exterior angle so formed is equal to the sum of the two interior opposite angles.