# Degrees or radians

Matteskolan shared this question 2 years ago

I rarely use GGB for simple trigonometric calculations, so I saw this just today: In GGB 6, if you enter "sin(3)" GGB interprets 3 as 3 degrees, but "sin(pi)" it interprets pi as radians. As "sin(3) in fact means sin(3 rad), this is a mathematical error. Pleeeease fix it! Pleeease!

Anders Karlsson

1

Bonjour ,

Une chance que qu'on n'ait pas cette anomalie en version 5 car elle risquerait de ne jamais être corrigée .

Espérons qu'elle soit rapidement corrigée en version 6 .

Cordialement

1

Merci. I don't read french, but I had your comment translated by someone who does.

1

I understand

But it is a very good pedagogic experimentation... It contributes to the development of critical thinking and favours open mindedness

First, students have to see that there is a problem with GeoGebra, and understand that : when it is a number (for example 30), it is degrees, and when it is a fraction of π, it is radians

and after that, they will never make the mistake in a mathematical exam (always write ° when degrees)

1

What!? Are you serious!? Radians need absolutely NOT be fractions of pi!

1

You need to select the main unit for angles, first.

Once you decided it, GeoGebra will use it as default.

If you set angles in radians, you can obtain also the trig values of angles in degrees simply by using the degrees symbol as you would do on paper.

To set your default angle unit:

Select the menu icon on top right, then Settings.

In the opening panel, on the right, select the last icon from top (the one with a cubic function on it). It's for the Algebra View preferences.

Choose your favourite angle unit from the displayed drop down list.

Close the panel and try entering a calculation containing angles in Algebra View. GeoGebra will use the selected unit (unless you enter the degrees symbol °)

1

@Matteskolan : Simona answered : if you want sin(3radians) use radians in preferences

(i didn't say that it is prohibited calculate sin(3radians) : but in all mathematical exercices, they never have to calculate sin(3radians). Angles are in degrees or in radians with fractions of π)

___________________________

Students with calculators CASIO or TI, always have to switch in preferences of calculator between degrees and radians, and they often make mistake when they ask for sin(30) (for sin(30degrees)) and the calculator is in radians, or if they ask for sin(π/6) (for sin(π/6radians) and the calculator is in degrees

With GeoGebra, sin(30) is sin(30degrees) and sin(π/6) is sin(π/6radians) : they first have to see it (reason why i told you it develop critical thinking...) after understanding this, it is very useful (for example verify if 30° is π/6)

You said it is a mathematical error. It is only a purpose of notation (as mathematicians often do isn't it..?) very useful