# Finding Reference Angle

• Mar 5th 2013, 02:42 PM
vaironxxrd
Finding Reference Angle
Hello again and again Everyone,

I'm having trouble finding a reference angle for the following angle.

$\theta = -1.8$

The book provides me with the answer which is $\theta' \approx 1.342$
But I cannot reach it, through my procedures.

I know the following is WRONG. But I'm trying to layout my method, to know where am I messing up.
I'm converting theta to be degrees, since it is easier for me.
-1.8 * 180 = -324
Angle coterminal to -324 = 36
Reference angle = 90 - 36
^- This is definitely wrong but I can't think of any other methods.
• Mar 5th 2013, 05:00 PM
topsquark
Re: Finding Reference Angle
Quote:

Originally Posted by vaironxxrd
Hello again and again Everyone,

I'm having trouble finding a reference angle for the following angle.

$\theta = -1.8$

The book provides me with the answer which is $\theta' \approx 1.342$
But I cannot reach it, through my procedures.

I know the following is WRONG. But I'm trying to layout my method, to know where am I messing up.
I'm converting theta to be degrees, since it is easier for me.
-1.8 * 180 = -324
Angle coterminal to -324 = 36
Reference angle = 90 - 36
^- This is definitely wrong but I can't think of any other methods.

Your angle is in quadrant IV so the reference angle of +324 would be 360 - 324 = 36.

Also, did you remember to convert back to radians?

-Dan
• Mar 5th 2013, 05:15 PM
Plato
Re: Finding Reference Angle
Quote:

Originally Posted by vaironxxrd
Hello again and again Everyone,
I'm having trouble finding a reference angle for the following angle.
$\theta = -1.8$
The book provides me with the answer which is $\theta' \approx 1.342$

Take a look at this webpage.

Because $\frac{\pi}{2}<1.8<\pi$ the reference angle is $\pi-1.8$.
• Mar 5th 2013, 05:29 PM
vaironxxrd
Re: Finding Reference Angle
Quote:

Originally Posted by Plato
Because $\frac{\pi}{2}<1.8<\pi$ the reference angle is $\pi-1.8$.