Add COS

STATUS.md

@@ -253,7 +253,7 @@ Floating point mathematical routines - not official, but well known and broadly
 | `$E097`   | `rnd_FAC1`             | DONE     |                                                    |
 | `$E09A`   | `rnd_A`                | DONE     |                                                    |
 | `$E0BE`   | `rnd_generate`         | DONE     |                                                    |
-| `$E264`   | `cos_FAC1`             | NOT DONE |                                                    |
+| `$E264`   | `cos_FAC1`             | PARTIAL  | needs `sin_FAC1`                                   |
 | `$E26B`   | `sin_FAC1`             | NOT DONE | some work already started                          |
 | `$E2B4`   | `tan_FAC1`             | NOT DONE |                                                    |
 | `$E30E`   | `atn_FAC1`             | NOT DONE |                                                    |

src/basic/math/e264.cos_FAC1.s

@@ -5,14 +5,17 @@
 ;
 ; Math package - cosine of FAC1 in radians
 ;
+; Adds pi/2 to FAC1 and falls through to the sine function
+;
 ; 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
-
 COS:
+    ldy #>const_HALF_PI
+    lda #<const_HALF_PI
+    jsr add_MEM_FAC1
     
-	+STUB_IMPLEMENTATION
+    ; FALLTHROUGH to SIN

strings/E02067B8

@@ -0,0 +1,3 @@
+$E0 + JSR $B867
+
+Fragment + call to well known floating point routine