NAG Library Routine Document

X02AHF

X02AHF returns the largest positive argument for which the Fortran intrinsic functions SIN and COS return a result with some meaningful accuracy.

The trigonometric functions $\sin$ and $\cos$ supplied in some compiler run-time libraries do not return accurate results when their argument is large. Often the related accuracy of a result gets progressively worse as the argument gets larger. X02AHF gives a value beyond which the compiler run-time library returns results with no relative accuracy at all. Note that some run-time libraries do return accurate results for all arguments to $\sin$ and $\cos$.

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See Section 9 in X02AJF.