Numbers and Angles
Numbers
You can create numbers by using the Input Bar. If you only type in a number (e.g. 3), GeoGebra assigns a lower case letter as the name of the number. If you want to give your number a specific name, you can type in the name followed by an equal sign and the number (e.g. create a decimal r by typing in r = 5.32).
In GeoGebra, numbers and angles use a period (.) as a decimal point. 
You can also use the constant π and the Euler constant e for expressions and calculations by selecting them from the drop down list next to the Input Bar or by using Keyboard Shortcuts.
If the variable e is not used as a name of an existing object yet, GeoGebra will recognize it as the Euler constant if you use it in new expressions. 
Angles
Angles can be entered in degrees (°) or radians (rad). The constant π is useful for radian values, and can also be entered as pi.
You can enter a degree symbol (°) or the pi symbol (π) by using the following keyboard shortcuts:


Angle α in degree
α = 60°
, or using the Degrees/Minutes/Seconds syntax:α =1°23′45''

Angle α in radians
α = pi/3
.
GeoGebra does all internal calculations in radians. The degree symbol (°) is nothing but the constant π/180 used to convert degree into radians. 

If a = 30 is a number, then α = a° converts number a to an angle α = 30°, without changing its value.

If you type in b = α / °, the angle α is converted back to the number b = 30, without changing its value.
For dependent angles you can specify whether they may become reflex or not on tab Basic of the Properties Dialog. 
Free Numbers and Angles
Free numbers and angles can be displayed as sliders in the Graphics View (see Slider Tool). Using the arrow keys, you may change the value of numbers and angles in the Algebra View too (see Manual Animation section).
Limit Value to Interval
Free numbers and angles may be limited to an interval [min, max] by using tab Slider of the Properties Dialog (see also Slider Tool).