kolibrios/programs/develop/ktcc/trunk/libc/math/acos.asm

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NASM
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format ELF
include 'proc32.inc'
section '.text' executable
public acos_ as "acos"
acos_:
; acos(x) = atan(sqrt((1-x*x)/(x*x)))
fld qword[esp+4]
fld st0 ;Duplicate X on tos.
fmul st0, st1 ;Compute X**2.
fld st0 ;Duplicate X**2 on tos.
fld1 ;Compute 1-X**2.
fsub st0, st1
fdiv st0, st1 ;Compute (1-x**2)/X**2.
fsqrt ;Compute sqrt((1-X**2)/X**2).
fld1 ;To compute full arctangent.
fpatan ;Compute atan of the above.
ret