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

[SpoonSamba]

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]

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.

 

[hopethisworks]

oooooooh dearrrrr

 

[SpoonSamba]

danz90 - Marry me?

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