[css-values-4] Add syntax for new math funcs.

Author: tabatkins

css-values-4/Overview.bs

@@ -2799,6 +2799,16 @@ Syntax</h3>
 	<<min()>>   = min( <<calc-sum>># )
 	<<max()>>   = max( <<calc-sum>># )
 	<<clamp()>> = clamp( <<calc-sum>>#{3} )
+	<<sin()>>   = sin( <<calc-sum>> )
+	<<cos()>>   = cos( <<calc-sum>> )
+	<<tan()>>   = tan( <<calc-sum>> )
+	<<asin()>>  = asin( <<calc-sum>> )
+	<<acos()>>  = acos( <<calc-sum>> )
+	<<atan()>>  = atan( <<calc-sum>> )
+	<<atan2()>> = atan2( <<calc-sum>>, <<calc-sum>> )
+	<<pow()>>   = pow( <<calc-sum>>, <<calc-sum>> )
+	<<sqrt()>>  = sqrt( <<calc-sum>> )
+	<<hypot()>> = hypot( <<calc-sum>># )
 	<dfn>&lt;calc-sum></dfn> = <<calc-product>> [ [ '+' | '-' ] <<calc-product>> ]*
 	<dfn>&lt;calc-product></dfn> = <<calc-value>> [ [ '*' | '/' ] <<calc-value>> ]*
 	<dfn>&lt;calc-value></dfn> = <<number>> | <<dimension>> | <<percentage>> | ( <<calc-sum>> )
@@ -2808,6 +2818,10 @@ Syntax</h3>
 	is required on both sides of the <css>+</css> and <css>-</css> operators.
 	(The <css>*</css> and <css>/</css> operaters can be used without white space around them.)
 
+	Several of the math functions above have additional constraints
+	on what their <<calc-sum>> arguments can contain.
+	Check the definitions of the individual functions for details.
+
 	UAs must support [=math function=] expressions of at least 20 terms,
 	where each <code>NUMBER</code>, <code>DIMENSION</code>, or <code>PERCENTAGE</code> is a term.
 	If a [=math function=] contains more than the supported number of terms,