Updated comment to trig functions to mention radians (#2825)

As discussed elsewhere,

there's only one way to specify argument for trig functions and we
already use it. We provide PI() so it should be convenient. Having said
that, degrees are taught in school, so the only reason we may consider
doing something about it is to facilitate education somehow.
I probably mentioned this before, but "radians" are just numbers. They
are ratios of two lengths. So, no matter the unit for the length, the
ration is just a number.
As for the issue, I don't see much harm in mentioning that we are using
radians. They are part of the International System of Units after all.
Although as a "derived unit". Degrees don't have the honor. They are
just "acceptable".
(https://www.bipm.org/documents/20126/41483022/SI-Brochure-9.pdf, page
145)

Resolves #2773

Co-authored-by: Dmitry Vasilevsky <[email protected]>

Author: DmitryVasilevsky

library/std/src/Std/Math.qs

@@ -250,79 +250,85 @@ function Min(values : Int[]) : Int {
 
 /// # Summary
 /// Returns the angle whose cosine is the specified number.
+/// Returned value is expressed in radians.
 function ArcCos(x : Double) : Double {
     body intrinsic;
 }
 
 /// # Summary
 /// Returns the angle whose sine is the specified number.
+/// Returned value is expressed in radians.
 function ArcSin(y : Double) : Double {
     body intrinsic;
 }
 
 /// # Summary
 /// Returns the angle whose tangent is the specified number.
+/// Returned value is expressed in radians.
 function ArcTan(d : Double) : Double {
     body intrinsic;
 }
 
 /// # Summary
 /// Returns the angle whose tangent is the quotient of two specified numbers.
+/// Returned value is expressed in radians.
 function ArcTan2(y : Double, x : Double) : Double {
     body intrinsic;
 }
 
 /// # Summary
 /// Returns the cosine of the specified angle.
+/// Angle is specified in radians.
 function Cos(theta : Double) : Double {
     body intrinsic;
 }
 
 /// # Summary
-/// Returns the hyperbolic cosine of the specified angle.
+/// Returns the hyperbolic cosine of the specified number.
 function Cosh(d : Double) : Double {
     body intrinsic;
 }
 
 /// # Summary
 /// Returns the sine of the specified angle.
+/// Angle is specified in radians.
 function Sin(theta : Double) : Double {
     body intrinsic;
 }
 
 /// # Summary
-/// Returns the hyperbolic sine of the specified angle.
+/// Returns the hyperbolic sine of the specified number.
 function Sinh(d : Double) : Double {
     body intrinsic;
 }
 
 /// # Summary
 /// Returns the tangent of the specified angle.
+/// Angle is specified in radians.
 function Tan(d : Double) : Double {
     body intrinsic;
 }
 
 /// # Summary
-/// Returns the hyperbolic tangent of the specified angle.
+/// Returns the hyperbolic tangent of the specified number.
 function Tanh(d : Double) : Double {
     body intrinsic;
 }
 
 /// # Summary
-/// Computes the inverse hyperbolic cosine of a number.
+/// Returns the inverse hyperbolic cosine of a number.
 function ArcCosh(x : Double) : Double {
     Log(x + Sqrt(x * x - 1.0))
 }
 
 /// # Summary
-/// Computes the inverse hyperbolic sine of a number.
+/// Returns the inverse hyperbolic sine of a number.
 function ArcSinh(x : Double) : Double {
     Log(x + Sqrt(x * x + 1.0))
 }
 
-
 /// # Summary
-/// Computes the inverse hyperbolic tangent of a number.
+/// Returns the inverse hyperbolic tangent of a number.
 function ArcTanh(x : Double) : Double {
     Log((1.0 + x) / (1.0 - x)) * 0.5
 }