Denis Bisson brought this to my attention:

If the Prime is in Degrees mode, the calculator will not draw an ellipse in the Plot Screen mode. Only points are plotted. Bisson provides an animated gif in the link below:

https://plus.google.com/+DenisBissonExpl...QCkHm16oob
Denis Bisson Wrote:It looks like the HP Prime doesn't draw "ellipse" in "Geometry" app when in CAS mode we're set in "Degree" but does work when we're set in "Radians". Is it normal? (Link)

At least for me isn't normal in any way. =( Confirmed too.

The geometry app is using the giac CAS for internal computation, ellipse is a CAS command, the display is obtained by a trigonometric parametrization of the ellipse. I can of course change the parametrization if the user is in degree mode, but like any CAS, giac is designed to work in radians not in degrees, I'm certain you would get problems later. There are a few functions that are also working in degree, but as soon as you are using non trivial functions, you should always use radian mode. Perhaps ellipse should force radian mode...

(11-11-2015 08:18 AM)parisse Wrote: [ -> ]Perhaps ellipse should force radian mode...

Best only internally without changing the user setting but just ignoring it.