CBSE Class 10 Mathematics Introduction To Trigonometry Notes

Class-X

Chapter 8:

Introduction to Trigonometry

Top Definitions

1. Trigonometry is the study of relationship between the sides and the angles of the triangle.

2. Ratio of the sides of the right triangle with respect to the acute angles is called trigonometric ratios of the angle.

3. Pythagoras theorem: In a right triangle, square of the hypotenuse is equal to the sum of the square of the other two sides.

Top Concepts

1. Trigonometry is the combination of three Greek words ‘Tri (Three) + gon (sides) + metron (measure)’.

2. When any two sides of a right triangle are given, its third side can be obtained by using Pythagoras theorem.

3. Angle measured in anticlockwise direction is taken as positive angle.

4. Angle measured in clockwise direction is taken as negative angle.

5. The values of the trigonometric ratios of an angle do not vary with the length of the sides of the triangle, if the angles remain the same.

6. The value of sin A or cos A never exceeds 1, whereas the value of sec A or cosec A is always greater than 1 or equal to 1.

7. Each trigonometric ratio is a real number. It has no unit.

8. Only symbol cosine, sine, tangent, cotangent, sec and cosec has no meaning.

9. (sinq)ⁿ sinq is generally written as sinⁿq , n being a positive integer. Similarly other trigonometric ratios can also be written. 

10. The value of sin q increases from 0 to 1 when q increases from 0⁰ to 90⁰.

11. The value of cos q decreases from 1 to 0 when q increases from 0⁰ to 90⁰.

Top Diagrams

1. Sides of right triangle

2. Values of Trigonometric ratios:

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