bpo-37548: Document range of atan, acos and asin (GH-14717)

potomak · mdickinson · commit dc3f99fa77f4 · 2019-07-13T14:59:55.000+01:00
diff --git a/Doc/library/math.rst b/Doc/library/math.rst
@@ -366,17 +366,20 @@ Trigonometric functions
 
 .. function:: acos(x)
 
-   Return the arc cosine of *x*, in radians.
+   Return the arc cosine of *x*, in radians. The result is between ``0`` and
+   ``pi``.
 
 
 .. function:: asin(x)
 
-   Return the arc sine of *x*, in radians.
+   Return the arc sine of *x*, in radians. The result is between ``-pi/2`` and
+   ``pi/2``.
 
 
 .. function:: atan(x)
 
-   Return the arc tangent of *x*, in radians.
+   Return the arc tangent of *x*, in radians. The result is between ``-pi/2`` and
+   ``pi/2``.
 
 
 .. function:: atan2(y, x)
diff --git a/Misc/ACKS b/Misc/ACKS
@@ -251,6 +251,7 @@ Jp Calderone
 Arnaud Calmettes
 Daniel Calvelo
 Tony Campbell
+Giovanni Cappellotto
 Brett Cannon
 Tristan Carel
 Mike Carlton
diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c
@@ -1072,19 +1072,22 @@ math_2(PyObject *const *args, Py_ssize_t nargs,
 
 FUNC1(acos, acos, 0,
       "acos($module, x, /)\n--\n\n"
-      "Return the arc cosine (measured in radians) of x.")
+      "Return the arc cosine (measured in radians) of x.\n\n"
+      "The result is between 0 and pi.")
 FUNC1(acosh, m_acosh, 0,
       "acosh($module, x, /)\n--\n\n"
       "Return the inverse hyperbolic cosine of x.")
 FUNC1(asin, asin, 0,
       "asin($module, x, /)\n--\n\n"
-      "Return the arc sine (measured in radians) of x.")
+      "Return the arc sine (measured in radians) of x.\n\n"
+      "The result is between -pi/2 and pi/2.")
 FUNC1(asinh, m_asinh, 0,
       "asinh($module, x, /)\n--\n\n"
       "Return the inverse hyperbolic sine of x.")
 FUNC1(atan, atan, 0,
       "atan($module, x, /)\n--\n\n"
-      "Return the arc tangent (measured in radians) of x.")
+      "Return the arc tangent (measured in radians) of x.\n\n"
+      "The result is between -pi/2 and pi/2.")
 FUNC2(atan2, m_atan2,
       "atan2($module, y, x, /)\n--\n\n"
       "Return the arc tangent (measured in radians) of y/x.\n\n"
