## ALP Programming Guide and Reference

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### Notes

If the operand is outside the acceptable range, the C2 flag is set, and ST remains unchanged. It is the programmer's responsibility to reduce the operand to an absolute value smaller than 263 by subtracting an appropriate integer multiple of 2ã. Refer to the Intel documentation 6 for a discussion of the proper value to use for ã in performing such reductions.

The fact that FPTAN pushes 1.0 onto the FPU stack after computing tan(ST) maintains compatibility with the 8087 and Intel287 math coprocessors, and simplifies the calculation of other trigonometric functions. For instance, the cotangent (which is the reciprocal of the tangent) can be computed by running FDIVR after FPTAN.

ST(7) must be empty to avoid an invalid-operation exception.