arccoshreturns the value of the inverse hyperbolic cosine, . The result is in the principal positive branch.
For full information please refer to the NAG Library document for s11ac
The argument of the function.
The value of the inverse hyperbolic cosine, .
- (errno )
On entry, .
The function has been called with an argument less than , for which is not defined.
arccoshcalculates an approximate value for the inverse hyperbolic cosine, . It is based on the relation
This form is used directly for , where , and the machine uses approximately decimal place arithmetic.
For , is equal to to within the accuracy of the machine and hence we can guard against premature overflow and, without loss of accuracy, calculate
NIST Digital Library of Mathematical Functions