Given: angle a b c and angle f g h are right angles; line segment b a is parallel to line segment g f; line segment b c is-congruent-to line segment g h prove: triangle a b c is-congruent-to triangle f g h triangles a b c and f g h are shown. triangle f g h is slightly lower and to the left of triangle a b c. lines extend from sides b a and g f to form parallel lines. another line connects points f and c. angles a b c and f g h are right angles. sides b c and g h are congruent. step 1: we know that angle a b c is-congruent-to angle f g h because all right angles are congruent. step 2: we know that angle b a c is-congruent-to angle g f h because corresponding angles of parallel lines are congruent. step 3: we know that line segment b c is-congruent-to line segment g h because it is given. step 4: triangle a b c is-congruent-to triangle f g h because of the asa congruence theorem. aas congruence theorem. third angle theorem. reflexive property.