$\"\"$

Given: $\"\"$ .

Prove: $\"\"$ $\"\"$

Proof:

Given that $\"\"$ . Since $\"\"$ forms a linear pair, sum of the measures of angles is 180. $\"\"$ .

Simillarly $\"\"$ forms a linear pair so sum of the measures of angles is 180, $\"\"$ . By transitive property, $\"\"$ .

Since $\"\"$ , $\"\"$ . By substitution and subtracton property we get $\"\"$ .

By the definition of congruent angles $\"\"$ .

$\"\"$ , by ASA postulate. $\"\"$

It is proved.