# New User - How do you create negative angle of rotation on the unit circle?

J F Ahearn shared this question 2 years ago

I am a new Geometry/Trigonometry teacher and also a new user to the Geogebra App and am trying to learn how to create a negative angle of rotation on a unit circle. Although there are many wonderful pre-existing models available for download and use, I would like to learn how to create the Geogebra model myfself. Unfortunately, I have spent the past 1.5 hours combing through the existing Questions in the topic bank and have not been able to find a reply which adequately addresses my situation. Nor have I been able to find a video on YouTube. Moreover, inspecting the Construction Protocols of several of the pre-existing models left me a bit overwhelmed by the various methods for obtaining the desired outcome.

My goal is to learn how to program Geogebra well enough to create solutions for my students - which are attending class virtually during the Covid Pandemic. The attached file contains an example of what I am trying to accomplish on page 3. I can create triangles on the unit circle using positive angles of rotation but do not know how to create a negative angle of rotation.

If anyone could direct me to a good resource which would allow me to obtain my goal, then I would be much obliged for a reply to this post.

Sincerely,

JF Ahearn

1

Please post your .ggb file so we can see how far you've got

Probably you need to put a point in the position you want for the negative angle eg

```P = (cos(-α), sin(-α))
```
then you can draw the angle in the position you want like

`Angle(P,(0,0), (1,0))`

1

Thank you for the quick reply and willingness to help. The attached file is very simple and I did not create any Trig functions.