The Unit Circle (part 2)

Last Friday we learned about the unit circle. Our formula in unit circle is X squared+ Y squared= 1. The standard position starts at (1,0).
In the CAST rule :
Quadrant I : sin(theta)- positive
cos(theta)-positive
tan(theta)-positive
Quadrant II : sin(theta)-positive
cos(theta)-negative
tan(theta)-negative
Quadrant III : sin(theta)-negative
cos(theta)-negative
tan(theta)-positive
Quadrant IV : sin(theta)-negative
cos(theta)-positive
tan(theta)-negative

Examples: 2 (stands for squared)
Find the sin(theta) in Quadrant I:
Given: (square root of 5, 2)
a2=b2=c2
square root of 5 squared=c2
5+4+c2
c2+square root of 9
=3
sin(theta)=O/H
=2/3

If (5/13, y) is a point on the unit circle in quadrant IV, find the value of y.
y=-12/13

The point P on the unit is NOT in Quadrant I. If sin(theta)=8/17, find the value of cos (theta).
cos (theta)=A/H
=-15/17

Find the tan(theta) in Quadrant II.
Given:(-4, 18)
tan(theta)=O/H
=-18/4 simplify: divide it to two.
=-9/2

Find the cos(theta) in Quadrant II.
given: (-3, 4)
cos(theta)= A/H
2 (stands for squared)
=a2+b2=c2
= -3 squared+ 4 squared=c2
=c2 square root= square root of 25
=5

cos(theta)= A/H
=-3/5