This document discusses triangles and congruence. It defines a triangle as a closed figure with three intersecting lines and as having three sides, three angles, and three vertices. It then explains the meaning of congruence as equal in all respects and introduces three rules for determining if triangles are congruent: the Side-Angle-Side rule, the Angle-Side-Angle rule, and the Angle-Angle-Side rule. The document concludes with assigning homework questions involving congruent triangles.

1. Chapter - 7
TRIANGLES
A closed figure formed by three intersecting lines is
called a triangle .
A triangle has three sides, three angles and three
vertices.
A
B
C
AB, BC, CA are the three sides, ∠A, ∠B, ∠ C are the three
angles and A, B, C are three vertices.

2. Meaning of ‘congruent’
Equal in all respects or figures whose shapes and
sizes are both the same
congruent figures

3. Find congruent figures

4. Symbol of congruence
≅
Note that in congruent triangles corresponding parts
are equal and we write in short ‘CPCT’ for
corresponding parts of congruent triangles.
Criteria for Congruence of Triangles

5. 1. SAS congruence rule :-
Two triangles are congruent if two sides and the included
angle of one triangle are equal to the sides and the
included angle of the other triangle.

6. 2. ASA congruence rule
Two triangles are congruent if two angles and the
included side of one triangle are equal to two angles
and the included side of other triangle.

7. 3. AAS Congruence Rule
Two triangles are congruent if any two pairs of angles
and one pair of corresponding sides are equal
AAS criterion for congruence of triangles is a
particular case of ASA criterion

8. 1. In quadrilateral ACBD, AC = AD and AB bisects A (see
Fig. ). Show that ▲ABC ≅▲ABD. What can you say about
BC and BD

9. Homework
1.
2.

10. Question .

11. Homework