diff --git a/CHANGES b/CHANGES
index 0cce4d2..9df9f1a 100644
--- a/CHANGES
+++ b/CHANGES
@@ -99,7 +99,7 @@ The following are the changes from calc version 2.14.3.5 to date:
     Document in help files for builtin functions that take eps arguments,
     the LIMIT range for such eps values.
 
-    Added new versin(x, [,eps]) for versed sine and vercos(x, [,eps])
+    Added new versin(x, [,eps]) for versed sine and coversin(x, [,eps])
     for versed cosine.
 
 
diff --git a/cal/regress.cal b/cal/regress.cal
index 8044520..83bfa6e 100644
--- a/cal/regress.cal
+++ b/cal/regress.cal
@@ -3533,31 +3533,31 @@ define test_trig()
 	    strcat(str(tnum++),
 		   ': round(versin(2 + 3i, 1e-10), 10) == 5.189625691+9.1092278938i'));
 
-	/* test versed cosine */
+	/* test coversed sine */
 	pi = pi(1e-20);
-	vrfy(round(vercos(0.2, 1e-10), 10) == 0.8013306692,
+	vrfy(round(coversin(0.2, 1e-10), 10) == 0.8013306692,
 	    strcat(str(tnum++),
-		   ': round(vercos(0.2, 1e-10), 10) == 0.8013306692'));
-	vrfy(round(vercos(3/7, 1e-10), 10) == 0.584428145,
+		   ': round(coversin(0.2, 1e-10), 10) == 0.8013306692'));
+	vrfy(round(coversin(3/7, 1e-10), 10) == 0.584428145,
 	    strcat(str(tnum++),
-		   ': round(vercos(3/7, 1e-10), 10) == 0.584428145'));
-	vrfy(round(vercos(-31, 1e-10), 10) == 0.5959623547,
+		   ': round(coversin(3/7, 1e-10), 10) == 0.584428145'));
+	vrfy(round(coversin(-31, 1e-10), 10) == 0.5959623547,
 	    strcat(str(tnum++),
-		   ': round(vercos(-31, 1e-10), 10) == 0.5959623547'));
-	vrfy(vercos(pi/6, 1e-10) == 0.5,
-				strcat(str(tnum++), ': vercos(pi/6, 1e-10) == 0.5'));
-	vrfy(vercos(pi/2, 1e-10) == 0,
-				strcat(str(tnum++), ': vercos(pi/2, 1e-10) == 0'));
-	vrfy(vercos(pi, 1e-10) == 1,
-				strcat(str(tnum++), ': vercos(pi, 1e-10) == 1'));
-	vrfy(vercos(3*pi/2, 1e-10) == 2,
-				strcat(str(tnum++), ': vercos(3*pi/2, 1e-10) == 2'));
-	vrfy(round(vercos(1, 1e-10), 10) == 0.1585290152,
+		   ': round(coversin(-31, 1e-10), 10) == 0.5959623547'));
+	vrfy(coversin(pi/6, 1e-10) == 0.5,
+				strcat(str(tnum++), ': coversin(pi/6, 1e-10) == 0.5'));
+	vrfy(coversin(pi/2, 1e-10) == 0,
+				strcat(str(tnum++), ': coversin(pi/2, 1e-10) == 0'));
+	vrfy(coversin(pi, 1e-10) == 1,
+				strcat(str(tnum++), ': coversin(pi, 1e-10) == 1'));
+	vrfy(coversin(3*pi/2, 1e-10) == 2,
+				strcat(str(tnum++), ': coversin(3*pi/2, 1e-10) == 2'));
+	vrfy(round(coversin(1, 1e-10), 10) == 0.1585290152,
 	    strcat(str(tnum++),
-		   ': round(vercos(1, 1e-10), 10) == 0.1585290152'));
-	vrfy(round(vercos(2 + 3i, 1e-10), 10) == -8.1544991469+4.16890696i,
+		   ': round(coversin(1, 1e-10), 10) == 0.1585290152'));
+	vrfy(round(coversin(2 + 3i, 1e-10), 10) == -8.1544991469+4.16890696i,
 	    strcat(str(tnum++),
-		   ': round(vercos(2 + 3i, 1e-10), 10) == -8.1544991469+4.16890696i'));
+		   ': round(coversin(2 + 3i, 1e-10), 10) == -8.1544991469+4.16890696i'));
 
 	print strcat(str(tnum++), ': Ending test_trig');
 }
diff --git a/calcerr.tbl b/calcerr.tbl
index d5c1560..0680dd2 100644
--- a/calcerr.tbl
+++ b/calcerr.tbl
@@ -553,6 +553,6 @@ E_LOGN_5	Non-numeric second argument for logn
 E_VERSIN1	Bad epsilon for versin
 E_VERSIN2	Bad first argument for versin
 E_VERSIN3	Too-large im(argument) for versin
-E_VERCOS1	Bad epsilon for vercos
-E_VERCOS2	Bad first argument for vercos
-E_VERCOS3	Too-large im(argument) for vercos
+E_COVERSIN1	Bad epsilon for coversin
+E_COVERSIN2	Bad first argument for coversin
+E_COVERSIN3	Too-large im(argument) for coversin
diff --git a/cmath.h b/cmath.h
index 2abeefc..8fcc752 100644
--- a/cmath.h
+++ b/cmath.h
@@ -119,7 +119,7 @@ E_FUNC COMPLEX *c_acsch(COMPLEX *c, NUMBER *epsilon);
 E_FUNC COMPLEX *c_gd(COMPLEX *c, NUMBER *epsilon);
 E_FUNC COMPLEX *c_agd(COMPLEX *c, NUMBER *epsilon);
 E_FUNC COMPLEX *c_versin(COMPLEX *c, NUMBER *epsilon);
-E_FUNC COMPLEX *c_vercos(COMPLEX *c, NUMBER *epsilon);
+E_FUNC COMPLEX *c_coversin(COMPLEX *c, NUMBER *epsilon);
 
 
 
diff --git a/comfunc.c b/comfunc.c
index 50dec9a..a7ff572 100644
--- a/comfunc.c
+++ b/comfunc.c
@@ -1371,10 +1371,10 @@ c_versin(COMPLEX *c, NUMBER *epsilon)
  *
  * This uses the formula:
  *
- *	vercos(x) = 1 - sin(x)
+ *	coversin(x) = 1 - sin(x)
  */
 COMPLEX *
-c_vercos(COMPLEX *c, NUMBER *epsilon)
+c_coversin(COMPLEX *c, NUMBER *epsilon)
 {
 	COMPLEX *r;		/* return COMPLEX value */
 	COMPLEX *ctmp;		/* complex sin(c) */
@@ -1387,7 +1387,7 @@ c_vercos(COMPLEX *c, NUMBER *epsilon)
 		not_reached();
 	}
 	if (check_epsilon(epsilon) == false) {
-		math_error("Invalid epsilon value for complex vercos");
+		math_error("Invalid epsilon value for complex coversin");
 		not_reached();
 	}
 
@@ -1396,7 +1396,7 @@ c_vercos(COMPLEX *c, NUMBER *epsilon)
 	 */
 	ctmp = c_sin(c, epsilon);
 	if (ctmp == NULL) {
-		math_error("Failed to compute complex sin for complex vercos");
+		math_error("Failed to compute complex sin for complex coversin");
 		not_reached();
 	}
 	r = c_sub(&_cone_, ctmp);
diff --git a/func.c b/func.c
index 2f8a990..5fda13f 100644
--- a/func.c
+++ b/func.c
@@ -3538,7 +3538,7 @@ f_versin(int count, VALUE **vals)
 
 
 S_FUNC VALUE
-f_vercos(int count, VALUE **vals)
+f_coversin(int count, VALUE **vals)
 {
 	VALUE result;
 	COMPLEX *c;
@@ -3555,7 +3555,7 @@ f_vercos(int count, VALUE **vals)
 	eps = conf->epsilon;
 	if (count == 2) {
 		if (verify_eps(vals[1]) == false) {
-			return error_value(E_VERCOS1);
+			return error_value(E_COVERSIN1);
 		}
 		eps = vals[1]->v_num;
 	}
@@ -3565,13 +3565,13 @@ f_vercos(int count, VALUE **vals)
 	 */
 	switch (vals[0]->v_type) {
 		case V_NUM:
-			result.v_num = qvercos(vals[0]->v_num, eps);
+			result.v_num = qcoversin(vals[0]->v_num, eps);
 			result.v_type = V_NUM;
 			break;
 		case V_COM:
-			c = c_vercos(vals[0]->v_com, eps);
+			c = c_coversin(vals[0]->v_com, eps);
 			if (c == NULL) {
-				return error_value(E_VERCOS3);
+				return error_value(E_COVERSIN3);
 			}
 			result.v_com = c;
 			result.v_type = V_COM;
@@ -3582,7 +3582,7 @@ f_vercos(int count, VALUE **vals)
 			}
 			break;
 		default:
-			return error_value(E_VERCOS2);
+			return error_value(E_COVERSIN2);
 	}
 	return result;
 }
@@ -10859,6 +10859,8 @@ STATIC CONST struct builtin builtins[] = {
 	 "hyperbolic cotangent of a within accuracy b"},
 	{"count", 2, 2, 0, OP_NOP, {.null = NULL}, {.valfunc_2 = f_count},
 	 "count listr/matrix elements satisfying some condition"},
+	{"coversin", 1, 2, 0, OP_NOP, {.null = NULL}, {.valfunc_cnt = f_coversin},
+	 "coversed sine of value a within accuracy b"},
 	{"cp", 2, 2, 0, OP_NOP, {.null = NULL}, {.valfunc_2 = f_cp},
 	 "cross product of two vectors"},
 	{"csc", 1, 2, 0, OP_NOP, {.null = NULL}, {.valfunc_cnt = f_csc},
@@ -11416,8 +11418,6 @@ STATIC CONST struct builtin builtins[] = {
 	 "unget char read from file"},
 	{"usertime", 0, 0, 0, OP_NOP, {.numfunc_0 = f_usertime}, {.null = NULL},
 	 "user mode CPU time in seconds"},
-	{"vercos", 1, 2, 0, OP_NOP, {.null = NULL}, {.valfunc_cnt = f_vercos},
-	 "versed cosine of value a within accuracy b"},
 	{"versin", 1, 2, 0, OP_NOP, {.null = NULL}, {.valfunc_cnt = f_versin},
 	 "versed sine of value a within accuracy b"},
 	{"version", 0, 0, 0, OP_NOP, {.null = NULL}, {.valfunc_0 = f_version},
diff --git a/help/Makefile b/help/Makefile
index d9d6e93..9d0f913 100644
--- a/help/Makefile
+++ b/help/Makefile
@@ -203,33 +203,33 @@ DETAIL_HELP= abs access acos acosh acot acoth acsc acsch address agd \
 	append appr arg argv arrow asec asech asin asinh assign atan atan2 \
 	atanh avg base base2 bernoulli bit blk blkcpy blkfree blocks bround \
 	btrunc calc_tty calclevel calcpath catalan ceil cfappr cfsim char \
-	cmdbuf cmp comb conj cos cosh cot coth count cp csc csch ctime d2dm \
-	d2dms d2g d2r delete den dereference det digit digits display dms2d dp \
-	epsilon errcount errmax errno error estr euler eval exp fact factor \
-	fclose fcnt feof ferror fflush fgetc fgetfield fgetfile fgetline fgets \
-	fgetstr fib files floor fopen forall fpathopen fprintf fputc fputs \
-	fputstr frac free freebernoulli freeeuler freeglobals freeredc \
-	freestatics frem freopen fscan fscanf fseek fsize ftell g2d g2gm g2gms \
-	g2r gcd gcdrem gd getenv gms2g h2hm h2hms hash head highbit hmean \
-	hms2h hnrmod hypot ilog ilog10 ilog2 im indices inputlevel insert int \
-	inverse iroot isalnum isalpha isassoc isatty isblk iscntrl isconfig \
-	isdefined isdigit iserror iseven isfile isgraph ishash isident isint \
-	islist islower ismat ismult isnull isnum isobj isobjtype isodd isprime \
-	isprint isptr ispunct isqrt isrand israndom isreal isrel issimple \
-	isspace issq isstr istype isupper isxdigit jacobi join lcm lcmfact \
-	lfactor ln log log2 logn lowbit ltol makelist matdim matfill matmax \
-	matmin matsum mattrace mattrans max memsize meq min minv mmin mne mod \
-	modify name near newerror nextcand nextprime norm null num oldvalue \
-	ord param perm pfact pi pix places pmod polar poly pop popcnt pound \
-	power prevcand prevprime printf prompt protect ptest push putenv quo \
-	quomod r2d r2g rand randbit random randombit randperm rcin rcmul rcout \
-	rcpow rcsq re remove reverse rewind rm root round rsearch runtime \
-	saveval scale scan scanf search sec sech seed segment select sgn sha1 \
-	sin sinh size sizeof sleep sort sqrt srand srandom ssq stoponerror str \
-	strcasecmp strcat strcmp strcpy strerror strlen strncasecmp strncmp \
-	strncpy strpos strprintf strscan strscanf strtolower strtoupper substr \
-	sum swap system systime tail tan tanh test time trunc usertime vercos \
-	versin version xor
+	cmdbuf cmp comb conj cos cosh cot coth count coversin cp csc csch \
+	ctime d2dm d2dms d2g d2r delete den dereference det digit digits \
+	display dms2d dp epsilon errcount errmax errno error estr euler eval \
+	exp fact factor fclose fcnt feof ferror fflush fgetc fgetfield \
+	fgetfile fgetline fgets fgetstr fib files floor fopen forall fpathopen \
+	fprintf fputc fputs fputstr frac free freebernoulli freeeuler \
+	freeglobals freeredc freestatics frem freopen fscan fscanf fseek fsize \
+	ftell g2d g2gm g2gms g2r gcd gcdrem gd getenv gms2g h2hm h2hms hash \
+	head highbit hmean hms2h hnrmod hypot ilog ilog10 ilog2 im indices \
+	inputlevel insert int inverse iroot isalnum isalpha isassoc isatty \
+	isblk iscntrl isconfig isdefined isdigit iserror iseven isfile isgraph \
+	ishash isident isint islist islower ismat ismult isnull isnum isobj \
+	isobjtype isodd isprime isprint isptr ispunct isqrt isrand israndom \
+	isreal isrel issimple isspace issq isstr istype isupper isxdigit \
+	jacobi join lcm lcmfact lfactor ln log log2 logn lowbit ltol makelist \
+	matdim matfill matmax matmin matsum mattrace mattrans max memsize meq \
+	min minv mmin mne mod modify name near newerror nextcand nextprime \
+	norm null num oldvalue ord param perm pfact pi pix places pmod polar \
+	poly pop popcnt pound power prevcand prevprime printf prompt protect \
+	ptest push putenv quo quomod r2d r2g rand randbit random randombit \
+	randperm rcin rcmul rcout rcpow rcsq re remove reverse rewind rm root \
+	round rsearch runtime saveval scale scan scanf search sec sech seed \
+	segment select sgn sha1 sin sinh size sizeof sleep sort sqrt srand \
+	srandom ssq stoponerror str strcasecmp strcat strcmp strcpy strerror \
+	strlen strncasecmp strncmp strncpy strpos strprintf strscan strscanf \
+	strtolower strtoupper substr sum swap system systime tail tan tanh \
+	test time trunc usertime versin version xor
 
 # This list is of files that are clones of DETAIL_HELP files.  They are
 # built from DETAIL_HELP files.
diff --git a/help/cos b/help/cos
index 6a7c921..34dc27f 100644
--- a/help/cos
+++ b/help/cos
@@ -34,7 +34,7 @@ LINK LIBRARY
 
 SEE ALSO
     sin, tan, sec, csc, cot, epsilon
-    versin, vercos
+    versin, coversin
 
 ## Copyright (C) 1999,2021,2023  Landon Curt Noll
 ##
diff --git a/help/cot b/help/cot
index 414d758..2863916 100644
--- a/help/cot
+++ b/help/cot
@@ -27,7 +27,7 @@ LINK LIBRARY
 
 SEE ALSO
     sin, cos, tan, sec, csc, epsilon
-    versin, vercos
+    versin, coversin
 
 ## Copyright (C) 1999,2021,2023  Landon Curt Noll
 ##
diff --git a/help/vercos b/help/coversin
similarity index 74%
rename from help/vercos
rename to help/coversin
index 4cac2e2..7870d3e 100644
--- a/help/vercos
+++ b/help/coversin
@@ -1,8 +1,8 @@
 NAME
-    vercos - versed cosine
+    coversin - coversed sine
 
 SYNOPSIS
-    vercos(x [,eps])
+    coversin(x [,eps])
 
 TYPES
     x		number (real or complex)
@@ -14,31 +14,31 @@ DESCRIPTION
     Calculate the versed cosine of x to a multiple of eps with error less in
     absolute value than .75 * eps.
 
-    The versed cosine function is sometimes called coversin, sometimes called cvs,
+    The coversed sine function is sometimes called covers, or cosiv, or cvs,
     may be defined as:
 
-    	vercos(x) = 1 - sin(x)
+	coversin(x) = 1 - sin(x)
 
 EXAMPLE
-    ; print vercos(0.2), vercos(3/7), vercos(-31)
+    ; print coversin(0.2), coversin(3/7), coversin(-31)
     0.80133066920493878454 0.58442814500694799193 0.59596235467693499395
 
-    ; print vercos(1, 1e-5), vercos(1, 1e-10), vercos(1, 1e-15), vercos(1, 1e-20)
+    ; print coversin(1, 1e-5), coversin(1, 1e-10), coversin(1, 1e-15), coversin(1, 1e-20)
     0.15853 0.1585290152 0.158529015192104 0.15852901519210349335
 
-    ; print vercos(2 + 3i, 1e-5), vercos(2 + 3i, 1e-10)
+    ; print coversin(2 + 3i, 1e-5), coversin(2 + 3i, 1e-10)
     -8.1545+4.16891i -8.1544991469+4.16890696i
 
     ; pi = pi(1e-20)
-    ; print vercos(pi/6, 1e-10), vercos(pi/2, 1e-10), vercos(pi, 1e-10), vercos(3*pi/2, 1e-10)
+    ; print coversin(pi/6, 1e-10), coversin(pi/2, 1e-10), coversin(pi, 1e-10), coversin(3*pi/2, 1e-10)
     0.5 0 1 2
 
 LIMITS
     0 < eps < 1
 
 LINK LIBRARY
-    NUMBER *qvercos(NUMBER *x, NUMBER *eps)
-    COMPLEX *c_vercos(COMPLEX *x, NUMBER *eps)
+    NUMBER *qcoversin(NUMBER *x, NUMBER *eps)
+    COMPLEX *c_coversin(COMPLEX *x, NUMBER *eps)
 
 SEE ALSO
     sin, cos, tan, sec, csc, cot, epsilon
diff --git a/help/csc b/help/csc
index 4b95241..f277ac0 100644
--- a/help/csc
+++ b/help/csc
@@ -26,7 +26,7 @@ LINK LIBRARY
 
 SEE ALSO
     sin, cos, tan, sec, cot, epsilon
-    versin, vercos
+    versin, coversin
 
 ## Copyright (C) 1999,2023  Landon Curt Noll
 ##
diff --git a/help/sec b/help/sec
index b563824..afdc317 100644
--- a/help/sec
+++ b/help/sec
@@ -27,7 +27,7 @@ LINK LIBRARY
 
 SEE ALSO
     sin, cos, tan, csc, cot, epsilon
-    versin, vercos
+    versin, coversin
 
 ## Copyright (C) 1999,2023  Landon Curt Noll
 ##
diff --git a/help/sin b/help/sin
index e8bfade..8272bdb 100644
--- a/help/sin
+++ b/help/sin
@@ -34,7 +34,7 @@ LINK LIBRARY
 
 SEE ALSO
     cos, tan, sec, csc, cot, epsilon
-    versin, vercos
+    versin, coversin
 
 ## Copyright (C) 1999,2021,2023  Landon Curt Noll
 ##
diff --git a/help/tan b/help/tan
index 5b17f82..ba7dd9e 100644
--- a/help/tan
+++ b/help/tan
@@ -28,7 +28,7 @@ LINK LIBRARY
 
 SEE ALSO
     sin, cos, sec, csc, cot, epsilon
-    versin, vercos
+    versin, coversin
 
 ## Copyright (C) 1999,2023  Landon Curt Noll
 ##
diff --git a/help/versin b/help/versin
index 9ae00d6..e6410e2 100644
--- a/help/versin
+++ b/help/versin
@@ -17,7 +17,7 @@ DESCRIPTION
     The versed sine function is sometimes called vers, sometimes called ver,
     may be defined as:
 
-    	versin(x) = 1 - cos(x)
+	versin(x) = 1 - cos(x)
 
 EXAMPLE
     ; print versin(0.2), versin(3/7), versin(-31)
@@ -42,7 +42,7 @@ LINK LIBRARY
 
 SEE ALSO
     sin, cos, tan, sec, csc, cot, epsilon
-    vercos
+    coversin
 
 ## Copyright (C) 2023  Landon Curt Noll
 ##
diff --git a/qmath.h b/qmath.h
index 21f9532..793a0e3 100644
--- a/qmath.h
+++ b/qmath.h
@@ -223,7 +223,7 @@ E_FUNC void qfreebern(void);
 E_FUNC NUMBER *qeuler(ZVALUE z);
 E_FUNC void qfreeeuler(void);
 E_FUNC NUMBER *qversin(NUMBER *q, NUMBER *epsilon);
-E_FUNC NUMBER *qvercos(NUMBER *q, NUMBER *epsilon);
+E_FUNC NUMBER *qcoversin(NUMBER *q, NUMBER *epsilon);
 
 
 /*
diff --git a/qtrans.c b/qtrans.c
index 179a164..4621de6 100644
--- a/qtrans.c
+++ b/qtrans.c
@@ -1977,7 +1977,9 @@ qacoth(NUMBER *q, NUMBER *epsilon)
 /*
  * versed sine - this calls qsincos() and discards the value of sin.
  *
- * This uses the formula: versin(x) = 1 - cos(x).
+ * This uses the formula:
+ *
+ *	versin(x) = 1 - cos(x)
  */
 NUMBER *
 qversin(NUMBER *q, NUMBER *epsilon)
@@ -2006,13 +2008,15 @@ qversin(NUMBER *q, NUMBER *epsilon)
 /*
  * versed cosine - this calls qsincos() and discards the value of cos.
  *
- * This uses the formula: vercos(x) = 1 - sin(x).
+ * This uses the formula:
+ *
+ *	coversin(x) = 1 - sin(x)
  */
 NUMBER *
-qvercos(NUMBER *q, NUMBER *epsilon)
+qcoversin(NUMBER *q, NUMBER *epsilon)
 {
 	NUMBER *sin, *cos, *res;
-	NUMBER *vercos;
+	NUMBER *coversin;
 	long n;
 
 	if (qiszero(epsilon)) {
@@ -2024,9 +2028,9 @@ qvercos(NUMBER *q, NUMBER *epsilon)
 		return qlink(&_qzero_);
 	qsincos(q, n + 2, &sin, &cos);
 	qfree(cos);
-	vercos = qsub(&_qone_, sin);
+	coversin = qsub(&_qone_, sin);
 	qfree(sin);
-	res = qmappr(vercos, epsilon, 24);
-	qfree(vercos);
+	res = qmappr(coversin, epsilon, 24);
+	qfree(coversin);
 	return res;
 }