2.	DEFB	+13,exponent+63
		DEFB	+0E,(+00,+00,+00)
	3.	DEFB	+55,exponent+65
		DEFB	+E4,+8D,(+00,+00)
	4.	DEFB	+58,exponent+68
		DEFB	+39,+BC,(+00,+00)
	5.	DEFB	+5B,exponent+6B
		DEFB	+98,+FD,(+00,+00)
	6.	DEFB	+9E,exponent+6E
		DEFB	+00,+36,+75,(+00)
	7.	DEFB	+A0,exponent+70
		DEFB	+DB,+E8,+B4,(+00)
	8.	DEFB	+63,exponent+73
		DEFB	+42,+C4,(+00,+00)
	9.	DEFB	+E6,exponent+76
		DEFB	+B5,+09,+36,+BE
	10.	DEFB	+E9,exponent+79
		DEFB	+36,+73,+1B,+5D
	11.	DEFB	+EC,exponent+7C
		DEFB	+D8,+DE,+63,+BE
	12.	DEFB	+F0,exponent+80
		DEFB	+61,+A1,+B3,+0C

At the end of the last loop the 'last value' is:

	ATN X/X	- case i.
	ATN (-1/X)/(-1/X)	- case ii.
	ATN (-1/X)/(-1/X)	- case iii.

Perform step iv.

		DEFB	+04,multiply	W, ATN X	- case i.
				W, ATN (-1/X)	- case ii.
				W, ATN (-1/X)	- case iii.
		DEFB	+0F,addition	ATN X - all cases now.
		DEFB	+38,end-calc	
		RET		Finished: 'last value' = ATX X.


THE 'ARCSIN' FUNCTION
(Offset 22: 'asn')

This subroutine handles the function ASN X and return a real real number from -PI/2 to PI/2 inclusive which is equal to the value in radians of the angle whose sine is X. Thereby if Y = ASN X then X = SIN Y.
This subroutine uses the trigonometric identity:
TAN (Y/2) = SIN Y/1(1+COS Y)
to obtain TAN (Y/2) and hence (using ATN) Y/2 and finally Y.

3833	asn	RST	0028,FP-CALC	X
		DEFB	+31,duplicate	X, X
		DEFB	+31,duplicate	X, X, X
		DEFB	+04,multiply	X, X*X
		DEFB	+A1,stk-one	X, X*X, 1
		DEFB	+03,subtract	X, X*X-1
		DEFB	+1B,negate	X,1-X*X
		DEFB	+28,sqr	X,SQR (1-X*X)
		DEFB	+A1,stk-one	X,SQR (1-X*X), 1
		DEFB	+0F,addition	X, 1+SQR (1-X*X)
		DEFB	+05,division	X/(1+SQR (1-X*X)) = TAN
				(Y/2)
		DEFB	+24,atn	Y/2
		DEFB	+31,duplicate	Y/2, Y/2
		DEFB	+0F,addition	Y = ASN X
		DEFB	+38,end-calc	
		RET		Finished: 'last value' = ASN X.