https://www.khanacademy.org/math/geometry/hs-geo-congruence/hs-geo-quadrilaterals-theorems/v/proof-opposite-sides-of-parallelogram-congruent 2021-02-16T16:08:12Z Proof: Opposite sides of a parallelogram Sal proves that a figure is a parallelogram if and only if opposite sides are congruent. Sal Khan video https://cdn.kastatic.org/googleusercontent/Aou3bes2NVoI_9-pt3FpYxyQjlLKBzk0bwXJZq0kKq94M8q29PBoRIhR6V-0z3AOc8Kl9JWtlmC8n0yfJP3JZJQ Proof: Opposite sides of a parallelogram Sal proves that a figure is a parallelogram if and only if opposite sides are congruent. https://cdn.kastatic.org/ka-youtube-converted/LhrGS4-Dd9I.mp4/LhrGS4-Dd9I.mp4 510 Quadrilaterals https://www.khanacademy.org/math/geometry/hs-geo-congruence/hs-geo-quadrilaterals-theorems/v/proof-opposite-angles-of-parallelogram-congruent 2021-02-16T16:08:13Z Proof: Opposite angles of a parallelogram Sal proves that opposite angles of a parallelogram are congruent. Sal Khan video https://cdn.kastatic.org/googleusercontent/6y9cgS_Ed8ofB7a7kabkdW7h8oxf3miLKnWKrP1ga4Us7tv5pMbOwfCP37w9HztilyNNuQKK2C0J_Slsai2VzgTd1g Proof: Opposite angles of a parallelogram Sal proves that opposite angles of a parallelogram are congruent. https://cdn.kastatic.org/ka-youtube-converted/oIV1zM8qlpk.mp4/oIV1zM8qlpk.mp4 248 Quadrilaterals https://www.khanacademy.org/math/geometry/hs-geo-congruence/hs-geo-quadrilaterals-theorems/v/proof-diagonals-of-a-parallelogram-bisect-each-other 2021-02-16T16:08:12Z Proof: Diagonals of a parallelogram Sal proves that a quadrilateral is a parallelogram if and only if its diagonals bisect each other. Sal Khan video https://cdn.kastatic.org/googleusercontent/BoWcWWoNIz6F-yhntRfgBQ16ESP1UFJk_C7gy5uwM6rrCwhcWmf0FcNBsncukkUxi-8eOJOwhbE-pNA3h4-UawCz Proof: Diagonals of a parallelogram Sal proves that a quadrilateral is a parallelogram if and only if its diagonals bisect each other. https://cdn.kastatic.org/ka-youtube-converted/TErJ-Yr67BI.mp4/TErJ-Yr67BI.mp4 546 Quadrilaterals https://www.khanacademy.org/math/geometry/hs-geo-congruence/hs-geo-quadrilaterals-theorems/v/proof-rhombus-diagonals-are-perpendicular-bisectors 2021-02-16T16:08:12Z Proof: Rhombus diagonals are perpendicular bisectors Sal proves that the diagonals of a rhombus are perpendicular, and that they intersect at the midpoints of both. Sal Khan video https://cdn.kastatic.org/googleusercontent/LQrBnagaN7-w5xyWQkeeTmgHttSnMTyzZpXBuIeMI4XA5UGHycO2sqqb56yHNoMSYrMZOty8gt9jMCgCjXy2wmap Proof: Rhombus diagonals are perpendicular bisectors Sal proves that the diagonals of a rhombus are perpendicular, and that they intersect at the midpoints of both. https://cdn.kastatic.org/ka-youtube-converted/GDcVdBAnBdU.mp4/GDcVdBAnBdU.mp4 244 Quadrilaterals https://www.khanacademy.org/math/ka-revision-class-9-math/x4d0389c6e7b01cca:week-2/x4d0389c6e7b01cca:quadrilaterals/e/revision-quadrilaterals-ncert-for-up-math-class-9 2026-04-07T23:55:07.30621384Z Revision Quadrilaterals . Aakash Bagga exercise