NCERT Book Class 11 Maths Chapter 3 Trigonometric Functions

Chapter 3
TRIGONOMETRIC FUNCTIONS
vA mathematician knows how to solve a problem,
he can not solve it. – MILNE v

3.1 Introduction
The word ‘trigonometry’ is derived from the Greek words
‘trigon’ and ‘metron’ and it means ‘measuring the sides of
a triangle’. The subject was originally developed to solve
geometric problems involving triangles. It was studied by
sea captains for navigation, surveyor to map out the new
lands, by engineers and others. Currently, trigonometry is
used in many areas such as the science of seismology,
designing electric circuits, describing the state of an atom,
predicting the heights of tides in the ocean, analysing a
musical tone and in many other areas.
In earlier classes, we have studied the trigonometric Arya Bhatt
ratios of acute angles as the ratio of the sides of a right (476-550)
angled triangle. We have also studied the trigonometric identities and application of
trigonometric ratios in solving the problems related to heights and distances. In this
Chapter, we will generalise the concept of trigonometric ratios to trigonometric functions
and study their properties.
3.2 Angles
Angle is a measure of rotation of a given ray about its initial point. The original ray is
Vertex

Fig 3.1