#12211: clarify math.copysign() documentation and docstring
diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c
index 4b3e642..00e2612 100644
--- a/Modules/mathmodule.c
+++ b/Modules/mathmodule.c
@@ -906,7 +906,11 @@
"This is the smallest integral value >= x.");
FUNC2(copysign, copysign,
- "copysign(x, y)\n\nReturn x with the sign of y.")
+ "copysign(x, y)\n\nReturn a float with the magnitude (absolute value) "
+ "of x but the sign \nof y. On platforms that support signed zeros, "
+ "copysign(1.0, -0.0) \nreturns -1.0.\n\n"
+ "If x is NaN, y is ignored and NaN is returned. If y is NaN, it is\n"
+ "treated as positive.")
FUNC1(cos, cos, 0,
"cos(x)\n\nReturn the cosine of x (measured in radians).")
FUNC1(cosh, cosh, 1,