2.2 Fundamental Relations between the trigonometic ratios of
an angle
From (3) we have, sec^{2}q 
tan^{2}q = 1 and
From (4) we have, cosec^{2}q
 cot^{2}q = 1
Trigonometric Functions Of Complementary Angles
let Ð OPM = a
so that (q + a)
= 90^{0} \ a
= (90  q)
Here q and a
are measures of complementary angles
Thus, in general :
sin q = cos (90  q)
cos q = sin (90  q)
tan q = cot (90  q)
cot q = tan (90  q)
sec q = cosec (90  q)
cosec q = sec (90  q)
These relations, associates the functions in pair
 (sine and cosine), (tangent and cotangent) and (secant and cosecant).
These three pairs of trigonometric functions are called "Cofunctions"

Index
2.1 Trigonometric Ratio of Acute Angles
2.2 Fundamental Relation between the trigonometric Ratios of an angle
2.3 Functions of General Angles or t Ratio
2.4 Tables of Trigonometric Function
Supplementary Problems
Chapter 3
