# Quadrilaterals Tutorial Series

Below are the tutorials on quadrilaterals. All links point videos on the **Sipnayan Youtube channel**.

Lesson 1: Basic Terminologies about Quadrilaterals

Lesson 2: Sum of the Interior Angles of Quadrilateral

Lesson 3: Definition of Parallelogram and Its Properties

Lesson 4: Proof that Opposite Sides of a Parallelogram are Congruent

Lesson 5: Proof that Opposite Angles of Parallelogram Are Congruent

Lesson 6: Proof that Diagonals of Parallelograms Divide it to Congruent Triangles

Lesson 7: Proof that Diagonals of a Parallelogram Bisect Each Other

Lesson 8: Proof that if Opposite Sides of a Quadrilateral are Congruent It is a Parallelogram

Lesson 9: Proof that if Opposite Angles of a Quadrilateral are Congruent It is a Parallelogram

Lesson 10: If the diagonals of a quadrilateral bisect each other, it is a parallelogram

Lesson 11: If one pair of sides of a quadrilateral are both congruent and parallel, it is a parallelogram

Lesson 12: Definitions of Rectangles, Rhombuses, and Squares

Lesson 13: Diagonals of a Rectangle are Congruent

Lesson 14: Diagonals of a Rhombus are Perpendicular

Lesson 15: Definition and Parts of a Trapezoid

Lesson 16: Base Angles of Isosceles Trapezoid are Congruent

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