Question

Prove that the sum of angles of a triangle is equal to two right angles

Answer 1

the sum of angles of a triangle = angleA + angleB + angleC = 180............(1)
right angle = 90 so, 2*90 = 180...........(2)
so sum of all the angles of a triangle from eqs 1 n 2 is 2*90 i.e. 2 right angles

Answer 2

Answer:

From External Angle of Triangle equals Sum of other Internal Angles: ∠ACD=∠ABC+∠BAC. ... But from Two Angles on Straight Line make Two Right Angles, ∠ACB+∠ACD equals two right angles. So by Euclid's First Common Notion, ∠ABC+∠BAC+∠ACB equals two right angles.