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 Summary ```#include <80c517.h> float acos517 ( float x); /* number to calculate arc cosine of */ ``` Description The acos517 function calculates the arc cosine of the floating-point number x. Note This routine uses the arithmetic unit of the Infineon C517x/C509 to provide accelerated execution speed. Do not use this routine with a CPU that does not support this feature. Return Value The acos517 function returns the arc cosine of x. For x ∈ [-1, 1], acos517(x) → [0, π]. For x ∈ (-∞, -1) ∪ (1, ∞), acos517(x) → NaN. See Also Example ```#include <80c517.h> #include /* for printf */ void tst_acos (void) { float x; float y; for (x = -1.0; x <= 1.0; x += 0.1) { y = acos517 (x); printf ("ACOS517(%f) = %f\n", x, y); } } ```

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