### CHAPTER AT A GLANCE

**1. Trigonometry**

Trigonometry is the study of relationships between the sides and angles of a right angled triangle.

**2. Trigonometric Ratios**

Trigonometric ratios of an acute angle in a right triangle express the relationship between the angle and the length of its sides.

Let ABC be a triangle right angled at B. Then the trigonometric ratios of the angle A in right DABC are defined as follows:

**4. Trigonometric Ratios of Complementary Angles:**We have the following relationship for complementary angles :

**5. Trigonometric Identities :**

An equation involving trigonometric ratios of an angle is called a trigonometric identity, if it is true for all values of the angle(s) involved

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