Minor mdoc fix.

lib/msun/man/cexp.3

@@ -59,17 +59,17 @@ behaves according to Euler's formula:
 .Bd -ragged -offset indent
 .Fn cexp "x + I*y"
 =
-.Ns ( Sy e Ns ** Ns
+.Po Sy e Ns ** Ns
 .Fa x *
-.Em cos Ns ( Ns
-.Fa y Ns )) + ( Ns
+.Em cos Ns Po Ns
+.Fa y Ns Pc Pc + Po Ns
 .Sy I
 *
 .Sy e Ns ** Ns
 .Fa x
 *
-.Em sin Ns ( Ns
-.Fa y Ns ))
+.Em sin Ns Po Ns
+.Fa y Ns Pc Pc
 .Ed
 .Pp
 Generally speaking, infinities, zeroes and \*(Nas are handled as would