SIN and COS Calculator

These routines calculate the signed 16-bit sine and cosine of an 8-bit angle. The returned value is a fixed point value with the point effectively being after the sign bit.
The code

;----------------------------------------------------------------	
;
; SIN(A) COS(A) routines. A full circle is represented by $00 to
; $00 in 256 1.40625 degree steps. returned value is signed 16
; bit with X being the high byte and ranges over +/-0.99997

; The routine never returns +1.0 as it is out of the range of the
; returned value. The routine also never returns -1.0 as, although
; it is in range, the calculation is symetrical for both positive
; and negative results.


;----------------------------------------------------------------
;
; get COS(A) in AX

cos_A
      CLC                     ; clear carry for add
      ADC   #$40              ; add 1/4 rotation

;----------------------------------------------------------------
;
; get SIN(A) in AX. enter with the Z flag reflecting the contents
; of A

sin_A
      BPL   sin_cos           ; just get SIN/COS and return if +ve

      AND   #$7F              ; else make +ve
      JSR   sin_cos           ; get SIN/COS
                              ; now do twos complement
      EOR   #$FF              ; toggle the low byte
      CLC                     ; clear carry for add
      ADC   #$01              ; add 1 to the low byte
      PHA                     ; save the low byte
      TXA                     ; copy the high byte
      EOR   #$FF              ; toggle the high byte
      ADC   #$00              ; add the carry from the low byte
      TAX                     ; copy back to X
      PLA                     ; restore the low byte
      RTS

;----------------------------------------------------------------
;
; get AX from SIN/COS table

sin_cos
      CMP   #$41              ; compare with max+1
      BCC   quadrant          ; branch if less

      EOR   #$7F              ; wrap $41 to $7F ..
      ADC   #$00              ; .. to $3F to $00
quadrant
      ASL                     ; * 2 bytes per value
      TAX                     ; copy to index
      LDA   sintab,X          ; get SIN/COS table value low byte
      PHA                     ; save it
      LDA   sintab+1,X        ; get SIN/COS table value high byte
      TAX                     ; copy to X
      PLA                     ; restore the low byte
      RTS

;----------------------------------------------------------------
;
; SIN/COS table. returns values between $0000 and $7FFF

sintab
      .word $0000,$0324,$0647,$096A,$0C8B,$0FAB,$12C8,$15E2
      .word $18F8,$1C0B,$1F19,$2223,$2528,$2826,$2B1F,$2E11
      .word $30FB,$33DE,$36BE,$398C,$3C56,$3F17,$41CE,$447A
      .word $471C,$49B4,$4C3F,$4EBF,$5133,$539B,$55F5,$5842
      .word $5A82,$5CB4,$5ED7,$60EC,$62F2,$64EB,$66CF,$68A6
      .word $6A6D,$6C24,$6DC4,$6F5F,$70E2,$7255,$73B5,$7504
      .word $7641,$776C,$7884,$798A,$7A7D,$7B5D,$7C2A,$7CE3
      .word $7D8A,$7E1D,$7E9D,$7F09,$7F62,$7FA7,$7FD8,$7FF6
      .word $7FFF

;----------------------------------------------------------------