Explain Trigonometry Angles

Introduction:   

  Trigonometry is that branch of mathematics which deals with the measurement of sides and angles of triangles and to similar triangles. 
Angles:

     An angle is an amount of rotation of a half-line (or ray) in a plane about its end point from an initial position to a terminal position. The important terms are: Measurement of angle, Positive and Negative angles, Lines at right angles, Quadrants, Angle in standard position. 

Measurement of Angles:
     To measure an angle we shall use two kinds of units, the degree unit and the radian unit.
     A degree(Sexagesimal system) is defined to be an angle formed by half-line (or a ray) rotated about its end point (1/360) of a complete revolution.
     Types of Angles: Acute angle, Obtuse angle, Right angle, Reflex angle, A straight angle. 
Radian Measure(Circular System)
     A radian is the measuring angles at the centre of a circle subtended by an arc, whose arc length and arc length formula is equal to the radius of the circle.