Page 164 - Start Up Mathematics_7

(ii) Right-angled triangle A

A triangle having one of its angles as right angle is known as a right-
angled triangle.

B C
(iii) Obtuse-angled triangle A
A triangle in which one angle is obtuse is known as an obtuse-
angled triangle.

B C
Example 1: Look at the following figures and classify each triangle on the basis of its

(a) sides. (b) angles.
P L

A
10 cm
5 cm 7 cm 8 cm 7 cm

B 7 cm C Q 6 cm R M 3 cm N
(i) (ii) (iii)
R
D X

6 cm 6 cm 7 cm
4 cm 6 cm

S 6 cm T E 4 cm F Y 6 cm Z

(iv) (v) (vi)

Solution: Figure (a) Classification according (b) Classification according
to sides to angles
(i) ∆ ABC Isosceles triangle Acute-angled triangle
(ii) ∆ PQR Scalene triangle Right-angled triangle
(iii) ∆ LMN Scalene triangle Obtuse-angled triangle
(iv) ∆ RST Equilateral triangle Acute-angled triangle
(v) ∆ DEF Isosceles triangle Obtuse-angled triangle
(vi) ∆ XYZ Isosceles triangle Right-angled triangle

A

Medians of a Triangle

Medians of a triangle are the line segments joining the vertices F E
of triangle to the midpoints of the opposite sides. G
In ∆ ABC, AD, BE and CF are the medians. The point of
intersection of the medians G is known as centroid. B D C

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