Add a missing doc (#53796)

putianyi889 · KristofferC · commit 7eeeb56a83cb · 2024-05-27T10:03:45.000+02:00
(cherry picked from commit 0c65f6f)
diff --git a/doc/src/base/math.md b/doc/src/base/math.md
@@ -70,6 +70,7 @@ Base.Math.tand
 Base.Math.sincosd
 Base.Math.sinpi
 Base.Math.cospi
+Base.Math.tanpi
 Base.Math.sincospi
 Base.sinh(::Number)
 Base.cosh(::Number)
