Question

The side BC of triangle ABC is produced on both sides. Prove that the sum of the two exterior
angles so formed is greater than 180°.​

Answer 1

Answer:

Given: Side BC of ABC is produced on both sides.

To prove: ext B + ext C > A

Proof:

ext B + ext C = 180o -B + 180o - C

= 360o - (B + C)

= 360o - (180o - A)

= 180o + A

Hence, ext B + ext C > A.