6. Isosceles and Equilateral Triangles
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| Statements | Reasons |
| QR ⊥ QT, ST ⊥ QT, QT∥ SR, △ VSR is isosceles with base SR, and QT∥ SR | Given |
| ∠ RQV and ∠ STV are right angles | Definition of perpendicular lines |
| ∠ RQV ≅ ∠ STV | All the right angles are congruent |
| VR ≅ VS | Definition of isosceles |
| ∠ VSR ≅ ∠ VRS | Isosceles Triangle Theorem |
| ∠ QVR ≅ ∠ VRS and ∠ TVS ≅ ∠ VSR | Alternate Interior Angle Theorem |
| ∠ QVR ≅ ∠ TVS | Transitive Property of Congruence |
| △ RQV ≅ △ STV | Angle-Angle-Side Theorem |