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:

- A column on the extreme left contains degree from 0° to 89°
- Ten columns for 0
^{’}, 6^{’}, 12^{’}, 18^{’}, 24^{’}, 30^{’}, 36^{’}, 42^{’}, 48^{’} and 54^{’}
- 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 0^{0},30^{0},45^{0},60^{0} and 90^{0} are useful angles in trigonometry, and their numerical values are easy to remember.

When two angles add up to 90^{0}, then any one angle is the complement of the other. Trigonometric ratios of complementary angles help in simplifying problems.

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:

- A column on the extreme left contains degree from 0° to 89°
- Ten columns for 0
^{’}, 6^{’}, 12^{’}, 18^{’}, 24^{’}, 30^{’}, 36^{’}, 42^{’}, 48^{’} and 54^{’}
- 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 0^{0},30^{0},45^{0},60^{0} and 90^{0} are useful angles in trigonometry, and their numerical values are easy to remember.

When two angles add up to 90^{0}, then any one angle is the complement of the other. Trigonometric ratios of complementary angles help in simplifying problems.

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