NCERT Book Class 10 Maths Chapter 8 Introduction to Trigonometry

INTRODUCTION TO TRIGONOMETRY 113

INTRODUCTION TO
TRIGONOMETRY 8
There is perhaps nothing which so occupies the
middle position of mathematics as trigonometry.
– J.F. Herbart (1890)
8.1 Introduction
You have already studied about triangles, and in particular, right triangles, in your
earlier classes. Let us take some examples from our surroundings where right triangles
can be imagined to be formed. For instance :
1. Suppose the students of a school are
visiting Qutub Minar. Now, if a student
is looking at the top of the Minar, a right
triangle can be imagined to be made,
as shown in Fig 8.1. Can the student
find out the height of the Minar, without
actually measuring it?
2. Suppose a girl is sitting on the balcony
of her house located on the bank of a Fig. 8.1
river. She is looking down at a flower
pot placed on a stair of a temple situated
nearby on the other bank of the river.
A right triangle is imagined to be made
in this situation as shown in Fig.8.2. If
you know the height at which the
person is sitting, can you find the width
of the river?
Fig. 8.2