The word
Trigonometry is derived from the Greek roots......'.tri' meaning ' three' , ' meaning
'an angle' ; and 'metron' meaning 'measure' . Thus ' trigonometry' means three angle measure. It is an analytical study of a three angled geometric figure_______namely the triangle.
We shall now learn the relations existing between the sides and angles of a right angled triangle.
RATIOS & FORMULAE :
SIN X , COS X , TAN X Where X is in degrees , their
reciprocals are Cosecant X, Secant X and Cotangent X
Sine
2 X + Cos
2 X = 1, Sec
2 X - Tan
2 X = 1 , Cosec
2 X - Cot
2 X = 1
Sin2A = 2 SinACosA, Cos 2A = Cos
2A - Sin
2A, Tan 2A = 2 tan A / 1- tan
2A