 # 10th Class Chapter No 20 - Trigonometrical Identities in Maths for ICSE

If an equation involving trigonometric ratios of an angle A is true for all values of A, then that equation is called a trigonometric identity.

#### Trigonometrical Tables

1. It is used to find the trigonometrical ratios of acute angles other than standard angles
2. It consists of three parts:

1. A column on the extreme left contains degree from 0° to 89°
2. Ten columns for 0, 6, 12, 18, 24, 30, 36, 42, 48 and 54
3. Five columns for 1, 2, 3, 4 and 5

The ratios of the sides in a right triangle with respect to its acute angles are called trigonometric ratios of the angle. The angles 00,300,450,600 and 900 are useful angles in trigonometry, and their numerical values are easy to remember.

When two angles add up to 900, then any one angle is the complement of the other. Trigonometric ratios of complementary angles help in simplifying problems.

Posted in 10th on July 11 2020 at 07:19 AM

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