Page 8 - Dahlia Oktaviani Ginting Buku

I a = a = I

60 =
cos
0
1
2
c
a 2a a
tan 30 = = = 1 3
0
b a 3 3
0
tan 60 = b = a 3 = 3
a a
c. 0 and 90 angle
0
0
To determine the trigonometric ratio of angles 0 and
0
90 use the unit circle in the Cartesian coordinate
0
system.
y

P(x,y)
1 y
 1 x
x
O Q

The point P(x,y) lies on the unit circle. The line OP forms
an angle with the X axis.  dengan sumbu X.
length OQ = unit
x
length PQ = unit and
y
length OP = 1 unit = circle radius.
 OPQ is a right triangle. Trigonometric ratios for angle
 with the X axis.
y x y
sin  = 1 ; cos  = 1 ; tan  = x

If = 0 , then the line OP coincides with the X axis with
0
P I (1 ,0 ) , consequently: I