Question

The given is: angle 1 is an exterior angle of triangle ABC
Prove: Measure of angle 1=m 13 years ago

Answer 1

Statement 1: (copy given) Reason: given
Statement 2: m<1 + m<2 = 180 Reason: def of supplementary angles
Statement 3: m<A + m<B + m<2 = 180 Reason: the sum of the measures of
the angles of a triangle equals 180
Statement 4: m<1 + m<2 = m<A + m<B + m<2 Reason: substitution
Statement 5: m<1 = m<A + m<B Reason: subtraction property of equality