Question

(10.03 HC) Look at the figure shown below.
A student made the table shown below to prove that XY is equal to YZ.
Sample Response

Statements Justifications
NY = MY
Given
m∡MYX = m∡NYZ
Given
m∡XNY = m∡ZMY
Given

m∡MYZ = m∡MYX + m∡XYZ
Angle Addition Postulate
m∡MYZ = m∡NYZ + m∡XYZ
Substitution
m∡NYX = m∡MYZ
Transitive Property
XYN ≅ ZYM
ASA postulate
XY = ZY
CPCTC

A. Provide the missing statement and justification in the proof.
B. Using complete sentences, explain why the proof would not work without the missing step.