3-186
INSTRUCTION SET REFERENCE
FCOSCosine
Description
This instruction calculates the cosine of the source operand in register ST(0) and stores the result
in ST(0). The source operand must be given in radians and must be within the range
?
2
63
to +2
63
.
The following table shows the results obtained when taking the cosine of various classes of
numbers, assuming that neither overflow nor underflow occurs.
NOTES:
FMeans finite-real number.
* Indicates floating-point invalid-arithmetic-operand (#IA) exception.
If the source operand is outside the acceptable range, the C2 flag in the FPU status word is set,
and the value in register ST(0) remains unchanged. The instruction does not raise an exception
when the source operand is out of range. It is up to the program to check the C2 flag for out-of-
range conditions. Source values outside the range
?
2
63
to +2
63
can be reduced to the range of the
instruction by subtracting an appropriate integer multiple of 2
?
or by using the FPREM instruc-
tion with a divisor of 2
?
. Refer to Section 7.5.8., Pi in Chapter 7, Floating-Point Unit of the Intel
Architecture Software Developers Manual, Volume 1, for a discussion of the proper value to use
for
?
in performing such reductions.
Operation
IF |ST(0)|
<
2
63
THEN
C2
<
0;
ST(0)
<
cosine(ST(0));
ELSE (*source operand is out-of-range *)
C2
<
1;
FI;
Opcode
Instruction
Description
D9 FF
FCOS
Replace ST(0) with its cosine
ST(0) SRC
ST(0) DEST
??
*
?
F
?
1 to +1
?
0
+1
+
0
+1
+F
?
1 to +1
+
?
*
NaN
NaN
