Helen's Holiday Blog #1

8-1

• To solve for theta you get the trig function by itself and then take an inverse.
• An inverse has 2 answers, find where the angle is based on trig function and if the number is positive or negative.
• Steps: Take the inverse of the postive # to find the QI angle.

To get to: QII: make negative, add 180 degrees
QIII: add 180 degrees
QIV: make negative, add 360 degrees

Examples:

1) 3cos(theta) +9=7
3cos(theta)=-2
cos(theta)=-2/3
theta=cos inverse (-2/3)
=48.1897 degrees
Answer: theta= 131.810,228.190


2) 5 sec (theta)+6=0
5 sec (theta)=-6
sec(theta)= -6/5
theta= sec inverse (6/5)
theta= cos inverse (5/6)

Answer: theta= 146.443,213.557