Question

what is the missing reason in the proof?
given: \\( \angle abc \\) is a right angle, \\( \angle dbc \\) is a straight angle
prove: \\( \angle abc \cong \angle abd \\)

Explanation:

The symmetric property of equality states that if \(a = b\), then \(b=a\). In step 7, we have \(m\angle ABD = 90^{\circ}\). Step 8, \(90^{\circ}=m\angle ABD\) is just a re - arrangement of the equation in step 7, which is exactly what the symmetric property of equality allows.

Answer:

Symmetric property of equality.