Question

prove that sum of all interior angles of a triangle is equal to 180 degree

Answer 1

try this by drawing the ext. angles and using ext angle property of triangle

Answer 2

Answer

According to the figure in attachment;

1 + 2 = 4 (exterior angle property)

4 = 180 - 3 (linear pair)

=> 1 + 2 = 180 - 3

=> 1 + 2 + 3 = 180

HENCE PROVED