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A function that can be used in Formulas.
arccos (x)
x.arccos (x) is defined for -1 ≤ x ≤ 1.
assert arccos (-1.1) = undefined
assert abs (arccos (-1.0) - pi) < 1e-17
assert abs (arccos (0.0) - pi/2) < 1e-17
assert arccos (1.0) = 0
assert arccos (1.1) = undefined
assert arccos (undefined) = undefined
© Paul Boersma 2023