Lines & Angles Class 9 Maths Notes | StudyTution

Complementary angles, Supplementary angles, Adjacent angles, Linear pair, Vertically opposite angles.

• If a ray stands on a line, then the adjacent angles so formed are supplementary and its converse,

• If two lines intersect, then vertically opposite angles are equal,

• If a transversal intersects two parallel lines, then

(i) corresponding angles are equal and conversely,

(ii) alternate interior angles are equal and conversely,

(iii) interior angles on the same side of the transversal are supplementary and conversely,

• Lines parallel to the same line are parallel to each other,

• Sum of the angles of a triangle is 180°,

• An exterior angle of a triangle is equal to the sum of the corresponding two interior opposite angles.