Chapter 3 - Trigonometric Functions

In the earlier classes all of us would have learnt the basic trigonometric ratios, which are nothing but ratios of the sides of triangle.
Let us go through just the basic formulas needed to remember for solving problems.

Angles
Angle is a measure of rotation given by the initial ray. It can be measured in degrees or in radians


Degree Measure
As mentioned, angle can be measured in degrees. Each degree can be divided into 60 minutes , also each minute is 60 seconds. 1° = 60’ and 1‘ = 60’’. Let us see some of the angle measures

Radian Measure
1 radian can be stated as the angle measure of the angle subtended by the arc of length 1 unit in a unit circle.
The formula essential here is θ = l/r or r = lθ
where l : arc length , r : radius of the circle, θ = angle subtended by the arc.

Relation between degree and radian
2Π = 360° , so Π = 180°. Or rather we can tell, 1 radian = (180 °)/Π
Based on this let us form the small table for important angles generally used