diff --git a/STATUS.md b/STATUS.md
index 53bab291..f6d74d3f 100644
--- a/STATUS.md
+++ b/STATUS.md
@@ -255,7 +255,7 @@ Floating point mathematical routines - not official, but well known and broadly
 | `$E0BE`   | `rnd_generate`         | DONE     |                                                    |
 | `$E264`   | `cos_FAC1`             | PARTIAL  | needs `sin_FAC1`                                   |
 | `$E26B`   | `sin_FAC1`             | NOT DONE | some work already started                          |
-| `$E2B4`   | `tan_FAC1`             | NOT DONE |                                                    |
+| `$E2B4`   | `tan_FAC1`             | PARTIAL  | not fully tested yet                               |
 | `$E30E`   | `atn_FAC1`             | NOT DONE |                                                    |
 
 <br />
diff --git a/src/basic/,stubs_math/e2b4.tan_FAC1.s b/src/basic/,stubs_math/e2b4.tan_FAC1.s
deleted file mode 100644
index 778ffa21..00000000
--- a/src/basic/,stubs_math/e2b4.tan_FAC1.s
+++ /dev/null
@@ -1,18 +0,0 @@
-;; #LAYOUT# STD *       #TAKE
-;; #LAYOUT# *   BASIC_0 #TAKE
-;; #LAYOUT# *   *       #IGNORE
-
-;
-; Math package - tangent of FAC1 in radians
-;
-; See also:
-; - [CM64] Computes Mapping the Commodore 64 - page 210
-; - https://www.c64-wiki.com/wiki/Floating_point_arithmetic
-; - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
-;
-
-; XXX provide implementation
-
-tan_FAC1:
-
-	+STUB_IMPLEMENTATION
diff --git a/src/basic/,stubs_math/e2b4.interop b/src/basic/math/e2b4.interop
similarity index 100%
rename from src/basic/,stubs_math/e2b4.interop
rename to src/basic/math/e2b4.interop
diff --git a/src/basic/math/e2b4.tan_FAC1.s b/src/basic/math/e2b4.tan_FAC1.s
new file mode 100644
index 00000000..7a9c6538
--- /dev/null
+++ b/src/basic/math/e2b4.tan_FAC1.s
@@ -0,0 +1,27 @@
+;; #LAYOUT# STD *       #TAKE
+;; #LAYOUT# *   BASIC_0 #TAKE
+;; #LAYOUT# *   *       #IGNORE
+
+;
+; Math package - tangent of FAC1 in radians
+;
+; See also:
+; - [CM64] Computes Mapping the Commodore 64 - page 210
+; - https://www.c64-wiki.com/wiki/Floating_point_arithmetic
+; - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
+; - https://www.c64-wiki.com/wiki/TAN
+
+; tan(x) = sin(x) / cos(x)
+
+tan_FAC1:
+    jsr mov_r_FAC1_TMP1         ; TMP1 = x
+    jsr sin_FAC1                ; FAC1 = sin(x)
+    jsr mov_r_FAC1_TMP2         ; TMP2 = sin(x)
+    lda #TEMPF1
+    ldy #0
+    jsr mov_MEM_FAC1            ; FAC1 = x
+    jsr COS                     ; FAC1 = cos(x)
+    lda #TEMPF2
+    ldy #0
+    jsr mov_MEM_FAC2            ; FAC2 = sin(x)
+    jmp div_FAC2_FAC1           ; FAC1 = tan(x)
diff --git a/strings/0020A2BB b/strings/0020A2BB
new file mode 100644
index 00000000..d49cc082
--- /dev/null
+++ b/strings/0020A2BB
@@ -0,0 +1,3 @@
+$00 + JSR $BBA2
+
+Fragment + call to well known floating point function
diff --git a/strings/1860202E b/strings/1860202E
new file mode 100644
index 00000000..7d6bffa4
--- /dev/null
+++ b/strings/1860202E
@@ -0,0 +1,3 @@
+CLC + RTS + JSR fragment
+
+Fragment of ending one function and beginning the next
diff --git a/strings/A957A000 b/strings/A957A000
new file mode 100644
index 00000000..b39ab76d
--- /dev/null
+++ b/strings/A957A000
@@ -0,0 +1,3 @@
+LDA #$57 + LDY #$00
+
+Load address of known zero page temporary floating point register into YA
diff --git a/strings/A957A00020A2BB b/strings/A957A00020A2BB
new file mode 100644
index 00000000..35470763
--- /dev/null
+++ b/strings/A957A00020A2BB
@@ -0,0 +1,3 @@
+LDA #$57 + LDY #$00 + JSR $BBA2
+
+Load adress of known temporary floating point register in zero page and call well known floating point function
diff --git a/strings/A95CA000 b/strings/A95CA000
new file mode 100644
index 00000000..ddd31646
--- /dev/null
+++ b/strings/A95CA000
@@ -0,0 +1,3 @@
+LDA #$5C + LDY #$00
+
+Load address of known zero page temporary floating point register into YA
diff --git a/strings/FFFF0000000000000000000000000000000000 b/strings/FFFF0000000000000000000000000000000000
new file mode 100644
index 00000000..caf8de5c
--- /dev/null
+++ b/strings/FFFF0000000000000000000000000000000000
@@ -0,0 +1,3 @@
+$FF followed by multiple 0's
+
+Meaningless - results of both ROM sets having empty space.