Use more maths to describe the fixed-point functions

This should help, I think?

man/rgbasm.5

@@ -403,17 +403,21 @@ The following functions are designed to operate with fixed-point numbers:
 .It Fn DIV x y Ta Fixed-point division
 .It Fn MUL x y Ta Fixed-point multiplication
 .It Fn FMOD x y Ta Fixed-point modulo
-.It Fn POW x y Ta $x$ to the $y$ power
-.It Fn LOG x y Ta Logarithm of $x$ to the base $y$
+.It Fn POW x y Ta $x sup y$
+.It Fn LOG x y Ta $log sub y ( x )$ (such that
+.Ic LOG Ns ( Ic POW Ns ( x , y ) , y ) == x)
 .It Fn ROUND x Ta Round $x$ to the nearest integer
-.It Fn CEIL x Ta Round $x$ up to an integer
-.It Fn FLOOR x Ta Round $x$ down to an integer
+.It Fn CEIL x Ta Round $x$ up to the nearest integer
+.It Fn FLOOR x Ta Round $x$ down to the nearest integer
 .It Fn SIN x Ta Sine of $x$
 .It Fn COS x Ta Cosine of $x$
 .It Fn TAN x Ta Tangent of $x$
-.It Fn ASIN x Ta Inverse sine of $x$
-.It Fn ACOS x Ta Inverse cosine of $x$
-.It Fn ATAN x Ta Inverse tangent of $x$
+.It Fn ASIN x Ta Inverse sine of $x$ (such that
+.Ic ASIN Ns ( Ic SIN Ns ( x ) ) == x)
+.It Fn ACOS x Ta Inverse cosine of $x$ (such that
+.Ic ACOS Ns ( Ic COS Ns ( x ) ) == x)
+.It Fn ATAN x Ta Inverse tangent of $x$ (such that
+.Ic ATAN Ns ( Ic TAN Ns ( x ) ) == x)
 .It Fn ATAN2 y x Ta Angle between $( x , y )$ and $( 1 , 0 )$
 .El
 .EQ