 
 
 
If you want to use a physical constants inside Xcas, put
it’s name between two characters _ 
("underscore"). Don’t confuse physical constants with symbolic constants, 
for example, e,π are symbolic constants as _c_,_NA_ are physical 
constants.
Input :
Output speed of light in vacuum :
^-1Input :
Output Avogadro’s number :
^-1 
 
