Option to choose default angle units

Thanks for this powerful library. I want to use evaluate function to compute math expressions.

Certain operators like sin, cos use default unit radian. For example: evaluate(sin(3.14/2)) gives 1. Can I change the default unit to the degree? e.g. evaluate(sin(90)) will give 1.

I think there should be a config to set the default units used in calculations.

[gwhitney]

TL;DR: The reason there is no “degree mode” in mathjs is that it is a very large amount of work, and it’s not clear how to get everything consistent (or whether it’s possible), and so the payoff has not been worth anyone’s effort when it’s pretty easy either to just write the units, define your own functions ‘cosd’ and ‘sind’ that take degrees, or use one of the other workarounds that have been posted in this issue.

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My full thoughts:

I wanted to add that adding a configuration setting for “degree” input to trigonometric functions is not as straightforward as it might seem. In a wide-ranging math library, not only do you have to modify the behavior of the six basic trigonometric functions, but also their inverses. And since we have derivative, well, the derivative of the sine function of angles measured in degrees is not cosine, even if you mean cosine of angles in degrees, it’s (π/180)*cosine. So you have to be very careful to change the derivative operation as well, for all affected functions. And what about polar coordinates? If angles are measured in degrees, all of the polar coordinate functions have to change their behavior as well. And since the exponential function for complex numbers is closely connected with trigonometric functions (exp(ia) = cos a + i sin a), the exponential function has to change its behavior too (euler’s formula becomes e^(180*i) + 1 = 0, for example). And that means that the power and log functions have to change also, so that they are consistent with exp. In fact, the majority of all mathematical operations on complex numbers have to change. I am not actually 100% certain there is a fully consistent set of mathematical operations on real and complex numbers in which one “measures angles in degrees.” I think it can be done, but there are many many details that would need tracking down.

So you see, there are very good reasons why mathematics as a whole measures angles in radians, and so why a computer math package that tries to cover a broad range of topics also measures angles in radians. It is very much not just an arbitrary choice.

In fact, I would say that mathjs goes farther than many general math packages in supporting degrees, by allowing expressions like cos(30 deg). Now that unicode is essentially universal, would it help to also support cos(30°) ? That would be quite easy and I would be glad to do it if it would be helpful.

[tobychidi-zz]

I wish this configuration support was ready. I am Working on a calculator plugin for a CBT system. Over here in Nigeria DEG is the default. I implemented my calculator with a simple evaluate(expression). Works like a charm except I can’t set default angles.

I think I need to understand that angles examples first.