# Formula and Concepts of Trigonometry

## Formula and Concepts of Trigonometry

TRIGNOMETRY-FORMULA AND CONCEPTS BY K.H. V.
AN ANGLE: An angle is the amount of rotation of a revolving line w.r.t a fixed straight line (a figure
formed by two rays having common initial point.) The two rays or lines are called the sides of the angle and common initial point is called the vertex of the angle. Rotation of the initial arm to the terminal arm generates the angle. +ve θ • Rotation can be anti clock wise or clockwise. angle • Angle is said to be +ve if rotation is anti clockwise. Initial • Angle is said to be -ve if rotation is clockwise. -ve angle side(arm)
T sid erm e( ina ar l m )

UNITS OF MEASUREMENT OF ANGLES: b) Centisimal system of angles: a) Sexagesimal system:
In sexagesimal system of measurement, the units of measurement are degrees, minutes and seconds. 1 right angle =90 degrees(90o); 1 degree = 60 minutes (60') 1 minute = 60 seconds (60'') 1 right angle =100 grades =100g 1 grade =100 minutes =100' 1' = 100 seconds =100''

c) RADIAN OR CIRCULAR MEASURE : In this system units of measurement is radian.
A radian is the measure of an angle subtended at the center of a circle by an arc whose length is equal to the radius of the circle. one radian is denoted by 1c

1 radian =570 161 22'' D B Arc ----r----- A

AB be the Arc, Let the length of the arc =OA=radius angle AOB =1 radian