Trigonometric functions

The relationship between trigonometric functions and a unit circle

A.V.Ali

www.2july-maths.co.uk

Take a circle with a radius equal to 1 unit

Mark a point, A, away from the circle

Now draw two tangents from A to the circle

A

1

Tangents to the circle

Radius of the circle

A secant line (the line of a chord through a circle)

sin, cos and tan function

Radius = 1

1a

aa

1

sin

bb

1

cosb

Radius = 1

c

cc

1

tan1

Radius = 1

cos

sin

tan

Summary

sec, cosec and cot function

Radius = 1

1

d

e

cottan

1

1tan

d

d

ece

e

cossin

1

1sin

Radius = 1

1

f

seccos

1

1cos

f

f

Radius = 1

sec

cosec

cot Summary