Question

WILL GIVE BRAINLIEST!!!!!!!!!

Answer 1

Answer:

Step-by-step explanation:

1). By definition of an exterior angle of a triangle,

  Measure of exterior angle of a triangle is equal to the sum of opposite two interior angles.

  From the figure attached,

  m∠4 = m∠1 + m∠2

2). Property of a triangle states that " sum of interior angles of a triangle is 180°"

   Therefore, m∠1 + m∠2 + m∠3 = 180°