Points a, b, and
form a triangle. complete the statements to prove that the sum of the interior angles of aabc is 180°.
1
statement
reason
points a, b, and c form a triangle.
given
let de be a line passing through b and parallel to ac. definition of parallel
23 25 and 21 24
m_1 = m 24 and m_3 = m25
m24+ m_2 + m25 = 180°
angle addition and definition of a straight line
m_1 + m2 + m23 = 180°
substitution