Introduction to Trigonometry

In this topic, we will use trigonometric ratios to find remaining sides and angles of a triangle when some of its sides and angles are given. It is done by using some ratios of sides of a triangle with respect to its acute angles.

In this topic, we shall find the trigonometric ratios of some standard angles 30, 60, 0 and 90 degrees and for 0 degree by using some elementary knowledge of geometry. For example, we can make use of the trigonometric tables.

In this topic, we will find the trigonometric ratios of complementary angles in terms of the trigonometric ratios of other given angles.

In this topic, we will prove one trigonometric identity, and use it further to prove other useful trigonometric identities. An equation involving trigonometric ratios of an angle is called a trigonometric identity.