MHB What is the reference angle for 60° and -60°?

[mathdad]

1. Find the reference angle given 60°.

Let R = reference angle

I decided to graph 60°. We are in Quadrant 1.

R = 90° - 60°

R = 30°

Book's answer for R is 60°.

2. Find the reference angle given - 60°.

I decided to graph - 60°. We are in Quadrant 4.

R = -90° - (-60°)

R = -90° + 60°

R = -30°

Book's answer for R is 60°.

 

[skeeter]

for $0 < \theta < 90$, reference angle is $\theta$

for $90 < \theta < 180$, reference angle is $180-\theta$

for $180 < \theta < 270$, reference angle is $\theta-180$

for $270 < \theta < 360$, reference angle is $360-\theta$

 

[mathdad]

Helpful picture reply.

Is there an algebraic method for finding the reference angle?

 

[skeeter]

Helpful picture reply.

Is there an algebraic method for finding the reference angle?

look at what I posted prior to the pic ...

 

[mathdad]

look at what I posted prior to the pic ...

I see it now. Thanks.