NAG CL Interface
s10abc (sinh)

Settings help

CL Name Style:

1 Purpose

s10abc returns the value of the hyperbolic sine, sinhx.

2 Specification

#include <nag.h>
double  s10abc (double x, NagError *fail)
The function may be called by the names: s10abc, nag_specfun_sinh or nag_sinh.

3 Description

s10abc calculates an approximate value for the hyperbolic sine of its argument, sinhx.
For |x|1 it uses the Chebyshev expansion
where t=2x2-1.
For 1<|x|E1,  sinhx=12(ex-e-x)
where E1 is a machine-dependent constant , details of which are given in the Users' Note for your implementation.
For |x|>E1, the function fails owing to the danger of setting overflow in calculating ex. The result returned for such calls is sinh(signxE1), i.e., it returns the result for the nearest valid argument.

4 References

NIST Digital Library of Mathematical Functions

5 Arguments

1: x double Input
On entry: the argument x of the function.
2: fail NagError * Input/Output
The NAG error argument (see Section 7 in the Introduction to the NAG Library CL Interface).

6 Error Indicators and Warnings

Dynamic memory allocation failed.
See Section 3.1.2 in the Introduction to the NAG Library CL Interface for further information.
An internal error has occurred in this function. Check the function call and any array sizes. If the call is correct then please contact NAG for assistance.
See Section 7.5 in the Introduction to the NAG Library CL Interface for further information.
Your licence key may have expired or may not have been installed correctly.
See Section 8 in the Introduction to the NAG Library CL Interface for further information.
On entry, x=value.
Constraint: |x|E1.
The function has been called with an argument too large in absolute magnitude. There is a danger of overflow. The result returned is the value of sinhx at the closest argument for which a valid call could be made.

7 Accuracy

If δ and ε are the relative errors in the argument and result, respectively, then in principle
|ε| |xcothx×δ|.  
That is the relative error in the argument, x, is amplified by a factor, approximately xcothx. The equality should hold if δ is greater than the machine precision (δ is a result of data errors etc.) but, if δ is simply a result of round-off in the machine representation of x, then it is possible that an extra figure may be lost in internal calculation round-off.
The behaviour of the error amplification factor can be seen in the following graph:
GnuplotProduced by GNUPLOT 5.4 patchlevel 6 100 101 0 1 2 3 4 5 6 7 8 9 ε/δ x x/tanh(x)
Figure 1
It should be noted that for |x|2
where Δ is the absolute error in the argument.

8 Parallelism and Performance

Background information to multithreading can be found in the Multithreading documentation.
s10abc is not threaded in any implementation.

9 Further Comments


10 Example

This example reads values of the argument x from a file, evaluates the function at each value of x and prints the results.

10.1 Program Text

Program Text (s10abce.c)

10.2 Program Data

Program Data (s10abce.d)

10.3 Program Results

Program Results (s10abce.r)