chore: import upstream snapshot with attribution

docs/functions/trigonometric.rst

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+Trigonometric functions
+-----------------------
+
+Except where otherwise noted, the trigonometric functions take a radian angle
+as input and the inverse trigonometric functions return radian angles.
+
+The ordinary trigonometric functions are single-valued functions defined
+everywhere in the complex plane (except at the poles of tan, sec, csc, and
+cot).  They are defined generally via the exponential function, e.g.
+
+.. math ::
+
+    \cos(x) = \frac{e^{ix} + e^{-ix}}{2}.
+
+The inverse trigonometric functions are multivalued, thus requiring branch
+cuts, and are generally real-valued only on a part of the real line.
+Definitions and branch cuts are given in the documentation of each function.
+The branch cut conventions used by mpmath are essentially the same as those
+found in most standard mathematical software, such as Mathematica and Python's
+own ``cmath`` libary.
+
+Degree-radian conversion
+........................
+
+.. autofunction:: mpmath.degrees
+.. autofunction:: mpmath.radians
+
+Trigonometric functions
+.......................
+
+.. autofunction:: mpmath.cos
+.. autofunction:: mpmath.sin
+.. autofunction:: mpmath.tan
+.. autofunction:: mpmath.sec
+.. autofunction:: mpmath.csc
+.. autofunction:: mpmath.cot
+
+
+Trigonometric functions with modified argument
+..............................................
+
+.. autofunction:: mpmath.cospi
+.. autofunction:: mpmath.sinpi
+
+
+Inverse trigonometric functions
+...............................
+
+.. autofunction:: mpmath.acos
+.. autofunction:: mpmath.asin
+.. autofunction:: mpmath.atan
+.. autofunction:: mpmath.atan2
+.. autofunction:: mpmath.asec
+.. autofunction:: mpmath.acsc
+.. autofunction:: mpmath.acot
+
+
+Sinc function
+.............
+
+.. autofunction:: mpmath.sinc
+.. autofunction:: mpmath.sincpi