A triangle is a three-sided shape. There are different types of triangles classified by their angles and sides, including scalene, isosceles, equilateral, acute, right, and obtuse triangles. Two figures are congruent if they have the same shape and size, with congruence symbolized by a tilde. Line segments and angles are congruent if their lengths or measures are equal, and triangles are congruent if one can be placed directly on top of the other to overlap completely.

2.  A triangle is a close figure
which is bounded by three
sides.
A
B C

3.  Scalene triangle
 Isosceles triangle
 Equilateral triangle

4.  Acute Angled Triangle
 Right Angled Triangle
 Obtuse Angled Triangle

5.  Two geometrical figures are
said to be congruent if they
have exactly the same shape
and size.
 The symbol of congruence is “ ”

6.  The line segments are
congruent if and only if their
lengths are equal.
A B C D

7.  Two angles are congruent if and
only if their measures are equal.
B
A C
E
D F

8.  Two triangles are congruent if and only if
one of them can be made to superpose
on the other, so as to cover it exactly.
A
B C
D
E F
ABC≡ DEF