Update library/math.po

Co-authored-by: Wei-Hsiang (Matt) Wang <mattwang44@gmail.com>

Author: Carisa-Li

library/math.po

@@ -281,7 +281,7 @@ msgstr "若 *x* 是正無限值或負無限值便回傳 ``True``，否則回傳
 msgid ""
 "Return ``True`` if *x* is a NaN (not a number), and ``False`` otherwise."
 msgstr ""
-"若 *x* 是 ``NaN`` ── 即非數字（not a number）── 便回傳 ``True``，否則回傳 "
+"若 *x* 是 ``NaN`` ── 即非數字（NaN, not a number）── 便回傳 ``True``，否則回傳 "
 "``False``。"
 
 #: ../../library/math.rst:192