Vertical angles theorem (top one): [tex]\angle 1 \cong \angle 3[/tex]
Given: [tex]\angle 1 \cong \angle 2[/tex]
Transitive property of congruence: [tex]\angle 3 \cong \angle 4[/tex]
Vertical angles theorem (bottom one): [tex]\angle 2 \cong \angle 4[/tex]
