Linear Equations in Two Variables
Introduction to Euclid’S Geometry
Lines and Angles
- Concept of Quadrilaterals - Sides, Adjacent Sides, Opposite Sides, Angle, Adjacent Angles and Opposite Angles
- Angle Sum Property 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
- Concept of Circle - Centre, Radius, Diameter, Arc, Sector, Chord, Segment, Semicircle, Circumference, Interior and Exterior, Concentric Circles
- Angle Subtended by a Chord at a Point
- Perpendicular from the Centre to a Chord
- Circles Passing Through One, Two, Three Points
- Equal Chords and Their Distances from the Centre
- Angle Subtended by an Arc of a Circle
- Cyclic Quadrilateral
Areas - Heron’S Formula
Surface Areas and Volumes
Statistics and Probability
Congruence of Triangles:
Two triangles are congruent if the sides and angles of one triangle are equal to the corresponding sides and angles of the other triangle.
△ ABC and △ PQR have the same size and shape. They are congruent.
△ABC ≅ △PQR
This means that, when you place △PQR on △ABC, P falls on A, Q falls on B and R falls on C, also PQ falls along `bar"AB", bar"QR" "falls along" bar"BC" and bar"PR" "falls along" bar"AC"`.
If, under a given correspondence, two triangles are congruent, then their corresponding parts (i.e., angles and sides) that match one another are equal.
Thus, in these two congruent triangles.
Corresponding vertices: A and P, B and Q, C, and R.
Corresponding sides: `bar"AB" and bar"PQ", bar"BC" and bar"QR", bar"AC" and bar"PR"`.
Corresponding angles: ∠A and ∠P, ∠B and ∠Q, ∠C, and ∠R.
Congruent triangles corresponding parts in short ‘CPCT’ stands for corresponding parts of congruent triangles.
∆ABC and ∆PQR are congruent under the correspondence:
ABC ↔ RQP
Write the parts of ∆ABC that correspond to
For a better understanding of the correspondence, let us use a diagram
The correspondence is ABC ↔ RQP.
This means A ↔ R; B ↔ Q; and C ↔ P.
(i) `bar"PQ" ↔ bar"CB"`
(ii) ∠Q ↔ ∠B and
(iii) `bar"RP" ↔ bar"AC"`.
Shaalaa.com | What is Congruence of Triangles?
State, whether the pairs of triangles given in the following figures are congruent or not:
Δ ABC in which AB = 2 cm, BC = 3.5 cm and ∠C = 80° and Δ DEF in which DE = 2 cm, DF = 3.5 cm and ∠D = 80°.