trigonometry half angle formulae

If ABC is a triangle with sides a = BC, b = CA, c = AB, then prove that where 2s = a + b + ..

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, Quadr..

Fig.(i) Fig.(ii) Fig.(iii) Let OA and OB two half lines with common end point O. The half lines OA and OB are the sides of an angle and the point O is the vertex of the angle. An angle is a..

The lines are said to be at right angles if the rotating half line (or ray) from starting from initial position to the final position describes one quarter of a circl..

A radian is the angle formed by a half line that has been rotated about its end point of a complete rotation. Let O be the centre of circle of radius r and if the circular arc AB is equal in length to the radius r of the circle, then by definition AB = 1 radi..

Measurement of Angles - To measure an angle we shall use two kinds of units, the degree unit and the radian un..

The amount of rotation from initial side to terminal is called the measure of an angle..

An angle whose measure is less than 90 o . (0 < q < ..

An angle whose measure is 90 o . ( q = 90 ..

Let O be the observer and P be the point under observation. Therefore, OP is the 'line of sight'. OQ is a line parallel to the horizontal plane. is called the angle of elevation. The point P, under observation, is at a higher level than the observer's positio..