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3843: THE 'ARCCOS' FUNCTION (offset +23)
The address of this routine is found in the table of addresses. It is called indirectly via fp_calc_2.
This subroutine handles the function ACS X and returns a real number from 0 to π inclusive which is equal to the value in radians of the angle whose cosine is X.
This subroutine uses the relation ACS X=π/2-ASN X.
acs 3843 RST $28 X
3844 DEFB $22 asn: ASN X
3845 DEFB $A3 stk_pi_2: ASN X, π/2
3846 DEFB $03 subtract: ASN X-π/2
3847 DEFB $1B negate: π/2-ASN X=ACS X
3848 DEFB $38 end_calc
3849 RET Finished: 'last value'=ACS X.
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