Activity Notes
Glossy
Classifying Quadrilaterals
Instruction
Active
Completing a Proof
Try it
Given: ABCD is a parallelogram.
Prove: m ZA+ m2B + m2C+ m2D = 360°
VN
D
By the definition of a parallelogram, AD//BC and
AB//DC. Using, AD as a transversal, ZA and 2
are same-side interior angles, so they are
By the definition of
supplementary, m ZA+ m2D = 180. Using side
as a transversal, ZB and 2C are same-side
interior angles, so they are supplementary. By the
definition of supplementary, m 2B + m2C = 180. So,
m ZA+ m2D + m2B + m2 = 180 + 180 by the
property. Simplifying, we have mZA
+ m2B + m2C + m2D = 360°.
A
B