What are the options (in most calculators) Deg and Rad used for? I activate one and the other and can't see any difference while calculating.
+118612 Deg stands for degrees and rad stands for radians.
They are different units to measure angles with.
Just like you can measure a distance with kilometers or with miles.
For normal maths operations like +. -, * divide etc you will see no difference but
if you are doing special angles things there is a big difference.
for instance
sin30 = 0.5 if the calc is set to degrees
BUT
sin30= -0.988 if the calc is set to radians
