Given: A quadrilateral, STVR exterior angle VRX. angle XRV is congruent to angle RST. angle RSV is congruent to angle TVS, To prove: RSTV is a parallelogram.1. angle XRV is congruent to angle RST | 1. given 2. VR is parallel to TS | 2. If a transversal, XS, intersects | two coplanar lines, VR and TS, and | a pair of corresponding angles-- | namely angles XRV and RST -- are | congruent, then the two coplanar | lines, VR and TS, are parallel. 3. angle RSV is congruent to angle TVS | 3. given 4. VT is parallel to RS | 4. If a transversal, VS, intersects | two coplanar lines, VT and RS, and | the alternate interior angles, RSV | and TVS are congruent, then the | the two coplanar lines, VT and RS, | are parallel. 5. RSTV is a parallogram. | 5. The definition of parallelogram: | A quadrilateral with each pair of | opposite sides, (VR and TS), and | (VT and RS), parallel. Edwin