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Coordinate Geometry
Introduction to Euclid’S Geometry
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Lines and Angles
- Introduction to Lines and Angles
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- Intersecting Lines and Non-intersecting Lines
- Introduction to Parallel Lines
- Pairs of Angles
- Parallel Lines and a Transversal
- Angle Sum Property of a Triangle
Triangles
- Concept of Triangles
- Congruence of Triangles
- Criteria for Congruence of Triangles
- Properties of a Triangle
- Some More Criteria for Congruence of Triangles
- Inequalities in a Triangle
Quadrilaterals
- Concept of Quadrilaterals
- Properties of a Quadrilateral
- Types of Quadrilaterals
- Another Condition for a Quadrilateral to Be a Parallelogram
- Theorem of Midpoints of Two Sides of a Triangle
- Property: The Opposite Sides of a Parallelogram Are of Equal Length.
- Theorem: A Diagonal of a Parallelogram Divides It into Two Congruent Triangles.
- Theorem : If Each Pair of Opposite Sides of a Quadrilateral is Equal, Then It is a Parallelogram.
- Property: The Opposite Angles of a Parallelogram Are of Equal Measure.
- Theorem: If in a Quadrilateral, Each Pair of Opposite Angles is Equal, Then It is a Parallelogram.
- Property: The diagonals of a parallelogram bisect each other. (at the point of their intersection)
- Theorem : If the Diagonals of a Quadrilateral Bisect Each Other, Then It is a Parallelogram
Circles
Areas - Heron’S Formula
Surface Areas and Volumes
Statistics
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- Introduction of Constructions
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Probability
Theorem
Theorem : If the diagonals of a quadrilateral bisect each other, then it is a parallelogram.
proof : 
In ∆ AOD and ∆ COB (Given)
OD = OB (Given)
∠AOB = ∠COD (Vertically opposite angles are equal)
Therefore , ∆AOD ≅ ∆COB (By SAS criterion of congruence)
So, ∠OAD = ∠OCB ...(1) (C.P.C.T)
Now , lines AC intersects AD and BC at A and C respectively,
such that ∠OAD = ∠OCB ...[from(1)]
`therefore` ∠OAD and ∠ OCB form a pair of alternate interior angles are equal.
Thus, AD || BC
Similarly , we can prove that AB || DC
Hence , quadrilatera; ABCD is a parallelogram.
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