math(3): Use the .Fa macro for function arguments

.Fa is the suitable macro for functions in comparsion to the
.Ar macro, which should be used for commandline arguments.

While here, fix some mandoc warnings.

Reviewed by:	imp (earlier version)
Obtained from:	OpenBSD (in partial)
MFC after:	3 days
Differential Revision:	https://reviews.freebsd.org/D31090

lib/msun/man/acos.3

@@ -60,7 +60,7 @@ These functions return the arc cosine in the range
 radians.
 If:
 .Bd -unfilled -offset indent
-.Pf \&| Ns Ar x Ns \&| > 1 ,
+.Pf \&| Ns Fa x Ns \&| > 1 ,
 .Ed
 .Pp
 .Fn acos x

lib/msun/man/acosh.3

@@ -55,13 +55,13 @@ and
 functions compute the inverse hyperbolic cosine
 of the real
 argument
-.Ar x .
+.Fa x .
 For a discussion of error due to roundoff, see
 .Xr math 3 .
 .Sh RETURN VALUES
 These functions
 return the inverse hyperbolic cosine of
-.Ar x .
+.Fa x .
 If the argument is less than 1,
 .Fn acosh
 raises an invalid exception and returns an \*(Na.

lib/msun/man/asin.3

@@ -62,7 +62,7 @@ These functions return the arc sine in the range
 radians.
 If:
 .Bd -unfilled -offset indent
-.Pf \&| Ns Ar x Ns \&| > 1
+.Pf \&| Ns Fa x Ns \&| > 1
 .Ed
 .Pp
 .Fn asin x

lib/msun/man/asinh.3

@@ -55,13 +55,13 @@ and
 functions compute the inverse hyperbolic sine
 of the real
 argument
-.Ar x .
+.Fa x .
 For a discussion of error due to roundoff, see
 .Xr math 3 .
 .Sh RETURN VALUES
 These functions
 return the inverse hyperbolic sine of
-.Ar x .
+.Fa x .
 .Sh SEE ALSO
 .Xr acosh 3 ,
 .Xr atanh 3 ,

lib/msun/man/atan2.3

@@ -63,7 +63,7 @@ The
 and
 .Fn atan2l
 functions compute the principal value of the arc tangent of
-.Fa y/ Ns Ar x ,
+.Fa y/ Ns Fa x ,
 using the signs of both arguments to determine the quadrant of
 the return value.
 .Pp
@@ -94,7 +94,7 @@ and
 .Fn atan2l
 functions, if successful,
 return the arc tangent of
-.Fa y/ Ns Ar x
+.Fa y/ Ns Fa x
 in the range
 .Bk -words
 .Bq \&- Ns \*(Pi , \&+ Ns \*(Pi
@@ -105,22 +105,22 @@ Here are some of the special cases:
 .It Fn atan2 y x No := Ta
 .Fn atan y/x Ta
 if
-.Ar x
+.Fa x
 > 0,
-.It Ta sign( Ns Ar y Ns )*(\*(Pi -
+.It Ta sign( Ns Fa y Ns )*(\*(Pi -
 .Fn atan "\*(Bay/x\*(Ba" ) Ta
 if
-.Ar x
+.Fa x
 < 0,
 .It Ta
 .No 0 Ta
 if x = y = 0, or
 .It Ta
-.Pf sign( Ar y Ns )*\*(Pi/2 Ta
+.Pf sign( Fa y Ns )*\*(Pi/2 Ta
 if
-.Ar x
+.Fa x
 = 0 \(!=
-.Ar y .
+.Fa y .
 .El
 .Sh NOTES
 The function

lib/msun/man/atanh.3

@@ -55,18 +55,18 @@ and
 functions compute the inverse hyperbolic tangent
 of the real
 argument
-.Ar x .
+.Fa x .
 For a discussion of error due to roundoff, see
 .Xr math 3 .
 .Sh RETURN VALUES
 These functions
 return the inverse hyperbolic tangent of
-.Ar x
+.Fa x
 if successful.
 If the argument has absolute value 1, a divide-by-zero exception
 is raised and an infinity is returned.
 If
-.Ar |x|
+.Fa |x|
 > 1, an invalid exception is raised and an \*(Na is returned.
 .Sh SEE ALSO
 .Xr acosh 3 ,

lib/msun/man/ccos.3

@@ -31,7 +31,7 @@
 .Nm ccos ,
 .Nm ccosf ,
 .Nm csin ,
-.Nm csinf
+.Nm csinf ,
 .Nm ctan ,
 .Nm ctanf
 .Nd complex trigonometric functions

lib/msun/man/ccosh.3

@@ -31,7 +31,7 @@
 .Nm ccosh ,
 .Nm ccoshf ,
 .Nm csinh ,
-.Nm csinhf
+.Nm csinhf ,
 .Nm ctanh ,
 .Nm ctanhf
 .Nd complex hyperbolic functions

lib/msun/man/exp.3

@@ -108,9 +108,9 @@ and the
 .Fn powl
 functions compute the value
 of
-.Ar x
+.Fa x
 to the exponent
-.Ar y .
+.Fa y .
 .Sh ERROR (due to Roundoff etc.)
 The values of
 .Fn exp 0 ,
@@ -181,8 +181,8 @@ then \*(Na**0 = 1 too because x**0 = 1 for all finite
 and infinite x, i.e., independently of x.
 .El
 .Sh SEE ALSO
-.Xr clog 3
+.Xr clog 3 ,
-.Xr cpow 3
+.Xr cpow 3 ,
 .Xr fenv 3 ,
 .Xr ldexp 3 ,
 .Xr log 3 ,

lib/msun/man/sincos.3

@@ -67,13 +67,13 @@ Upon returning from
 and
 .Fn sincosl ,
 the memory pointed to by
-.Ar "*s"
+.Fa "*s"
 and
-.Ar "*c"
+.Fa "*c"
 are assigned the values of sine and cosine, respectively.
 .Sh SEE ALSO
 .Xr cos 3 ,
-.Xr sin 3 ,
+.Xr sin 3
 .Sh HISTORY
 These functions were added to
 .Fx 9.0

lib/msun/man/sqrt.3

@@ -63,7 +63,7 @@ and
 .Fn cbrtl
 functions compute
 the cube root of
-.Ar x .
+.Fa x .
 .Pp
 The
 .Fn sqrt ,
@@ -72,7 +72,7 @@ and
 .Fn sqrtl
 functions compute the
 non-negative square root of
-.Ar x .
+.Fa x .
 .Sh RETURN VALUES
 The
 .Fn cbrt ,