Page 90 - Math SL HB Sem 1
P. 90
CIRCULAR FUNCTIONS AND TRIGONOMETRY
DEFINITION OF TRIGONOME'IRIC RATIOS IN TERMS OF THE UNIT
CICLE
Let the point P (x,y) be a point on the circumference ofthe unit circle,
x'+ y'= I with the centre of the origin (0,0) and radius I unit
vl
J)
v
.!M
MP
sln a = __ v figure 7
OP
-MO
cos A:
OP
In the first quadrant we extend Op to mee t the
tangent at A( I ,0) so that it meets this tangent at
e.
Q's position relative to A is defined as the tangent
function
AQ NP AQ sind
l.c
OA ON I cos d
v
Q(1, tan 0)
lznO
sin0
I
I
N 0)
cos0
figure 8
tind
Therefore, tro d =
cos d
+-o
