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diff --git a/sw/f4/FRTSRC/sin.ra b/sw/f4/FRTSRC/sin.ra
new file mode 100644
index 0000000..bf938a1
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+++ b/sw/f4/FRTSRC/sin.ra
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+/
+/
+/	S  I  N
+/	-  -  -
+/
+/SUBROUTINE	SIN(X)
+/
+/ VERSION 5A 4-27-77  PT
+/
+	SECT	SIN
+	JA	#SIN
+	EXTERN	#ARGER
+SINER,	TRAP4	#ARGER
+	TEXT	+SIN   +
+SINXR,	SETX	XRSIN
+	SETB	BPSIN
+BPSIN,	F 0.0
+XRSIN,	F 0.0
+SIN1,	F 0.0
+SIN2,	F 0.0
+F1SIN,	F 1.
+FPI2SN,	1		/PI DIVIDED BY 2
+	3110
+	3755
+FPISIN,	2		/PI
+	3110
+	3755
+F2PISN,	3		/TWO PI
+	3110
+	3755
+	ORG	10*3+BPSIN
+	FNOP
+	JA 	SINXR
+	0
+SINRTN,	JA	.
+/
+SINC9,	7764
+	2501
+	7015
+/
+SINC7,	7771
+	5464
+	5515
+/
+SINC5,	7775
+	2431
+	5362
+/
+SINC3,	0000
+	5325
+	0414
+/
+SINTST,	7770
+	2000
+	0000
+	BASE	0
+#SIN,	STARTD
+	FLDA	10*3
+	FSTA	SINRTN
+	FLDA	0
+	SETX	XRSIN
+	SETB	BPSIN
+	BASE	BPSIN
+	LDX	1,1	
+	FSTA	BPSIN
+	FLDA%	BPSIN,1  /ADDR OF X
+	FSTA	BPSIN
+	STARTF
+	FLDA%	BPSIN	/GET X
+	LDX	-1,0		/SET SIGN TO POSITIVE.
+	JGT	SINMOD		/IF POSITIVE BYPASS FUDGE.
+	JEQ	SINRTN		/IF ZERO EXIT.
+	FNEG			/NEGATIVE. NEGATE AC. SIN(-X)=-SIN(X)
+	LDX	0,0		/SET SIGN TO MINUS.
+SINMOD,	JAL	SINER		/IF SIGN CAN T INT, THEN ERROR.
+	FDIV	F2PISN		/REDUCE TO BELOW TWO PI.
+	FSTA	SIN1		/SAVE IN A TEMP.
+	ALN	0
+	FNORM			/INTERGIZE IT.
+	FNEG
+	FADD	SIN1		/RECALL NUMBER. AC NOW <0
+	FMUL	F2PISN		/NOW MULTIPLY BACK.
+	FSTA	SIN2		/AND SAVE AWAY.
+	FSUB	FPISIN		/SUBTRACT OFF PI.
+	JLT	SINP		/LESS THEN PI.
+	FSTA	SIN2		/RESTORE AS 2.
+	XTA	0		/INVERT THE SIGN.
+	FNEG
+	FSUB	F1SIN		/SIN(X-PI)=-SIN(X)
+	ATX	0		/AND PUT BACK.
+/
+SINP,	FLDA	SIN2		/RECALL MAGIC GOODY.
+	FSUB	FPI2SN		/TEST TO SEE IF X<PI/2
+	JLT	SINPP		/YEP.
+/
+	FLDA	FPISIN		/SIN(X)=SIN(PI-X)
+	FSUB	SIN2
+	FSTA	SIN2		/AND STORE IT BACK.
+/
+SINPP,	FLDA	SIN2		/GET THE MAGIC NUMBER.
+	FSUB	SINTST		/SEE IF ITS CLOSE TO AN EDGE
+	JGT	SINPPP		/IT IS NOT
+	FLDA	SIN2		/RECALL NUMBER IF TOO SMALE
+	JXN	SINRTN,0		/EXIT IF SAME SIGN.
+	FNEG			/ELSE NEGATE IT.
+	JA	SINRTN
+SINPPP,	FLDA	SIN2		/RECALL NUMBER TO BE WORKED ON.
+	FDIV	FPI2SN		/DIVIDE BY PI OVER TWO.
+	FSTA	SIN2		/AND STORE BACK.
+	FMUL	SIN2		/MULTIPLY OUT.
+	FSTA	SIN1
+	FMUL	SINC9		/NOW DO THE STANDARD ITERATION.
+	FADD	SINC7
+	FMUL	SIN1
+	FADD	SINC5
+	FMUL	SIN1
+	FADD	SINC3
+	FMUL	SIN1
+	FADD	FPI2SN		/ADD IN PI OVER 2
+	FMUL	SIN2		/DO THE FINAL MULTIPLY.
+	JXN	SINRTN,0		/SHALL WE NEGATE
+	FNEG			/YEP
+	JA	SINRTN		/AND RETURN.
+