• Best of luck to the class of 2024 for their HSC exams. You got this!
    Let us know your thoughts on the HSC exams here
  • YOU can help the next generation of students in the community!
    Share your trial papers and notes on our Notes & Resources page
MedVision ad

Trig Functions HELP WTF IS THE CIRCLE THING!!! (1 Viewer)

SpoonSamba

Member
Joined
Jan 30, 2008
Messages
280
Gender
Female
HSC
2008
okay you know how when you solve trig functions you have to use the circle thing with the quadrants and stuff to get an answer?

When do i use the circle thing?

When my teacher does it on the board i get so confused I just dont know when to turn to it'

and the only thing i can identify from it is if the function is negative or positive but i really have no idea how it works

SO WHO CAN EXPLAIN THE CIRCLE THING!
 

danz90

Active Member
Joined
Feb 2, 2007
Messages
1,467
Location
Sydney
Gender
Male
HSC
2008
When you're given a trig equation to solve
e.g. 1-2cosx=0
2cosx=1
cosx=1/2
you have to look at the value of cosx.. eg. in this case, 1/2 is a positive value. Therefore, you have to look with the circle thing (All Stations To Central) , where COS is positive. Here's a simple diagram I drew with paint.



First quadrant: A - All are positive. Angle= x (basic angle)
Second quadrant: S - only Sin is positive, all others are neg. Angle = 180-x
Third quadrant: T - only Tan is positive, all others are neg. Angle = 180 + x
Fourth Quadrant: C - only Cos is positive, all others are neg. Angle = 360 - x

With the example I gave, you have to see where Cos is positive. Cos is +ve in the fourth quadrant, and first quadrant.

Cos x = 1/2
x = 60° (1st quadrant)

your 2nd solution is where cos is positive again: in 4th quadrant
2nd soln = 360 - x
= 360 - 60
= 300°

therefore, your soln for 1-2cosx=0 is 60°, 300°

Hope that helps.
 

SpoonSamba

Member
Joined
Jan 30, 2008
Messages
280
Gender
Female
HSC
2008
danz90 - Marry me?

Im printing out your reply and gonna try a few questions. I'll see how i go :D
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top