Question

using the exterior angle inequality prove the sum of the measures of any 2 angles of a triangle is less than 180.

Answer 1

exterior angle theorem states that the measure of any exterior angle is greater than both of the non-adjacent interior angle

all angles in a triangle add up to 180^o

M<ACD>M<CAB and M<ACD>M<ABC

angle 4 is greater than angle 1 and angle 2