Intel ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS MANUAL VOLUME 1 REV 2.3 Manual page 1420

FCOS—Cosine
Opcode
D9 FF
Description
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 . The following table shows the results obtained when taking the cosine of
various classes of numbers, assuming that neither overflow nor underflow occurs.
ST(0) SRC
NaN
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
integer multiple of 2 or by using the FPREM instruction with a divisor of 2.
Operation
IF |ST(0)|  2
THEN
C2  0;
ST(0)  cosine(ST(0));
ELSE (*source operand is out-of-range *)
C2  1;
FI;
4:118
Instruction
FCOS
ST(0) DEST

*
 F  1 to +1
 0
+1
 0
+1
 1 to +1
+F
+ 
*
NaN
can be reduced to the range of the instruction by subtracting an appropriate
63
Description
Replace ST(0) with its cosine
Volume 4: Base IA-32 Instruction Reference
63
63