asinh

Calculates the inverse hyperbolic sine of a number

```include <math.h>
double asinh ( double x  );
float asinhf ( float x  );
long double asinhl ( long double x  );
```

The asinh( ) functions return the number whose hyperbolic sine is equal to the argument x.

#### Example

```puts("   x          asinh(x)        log( x + sqrt(x*x+1))\n"
"-------------------------------------------------------");
for ( double x = -2.0; x < 2.1; x += 0.5)
printf("%6.2f %15f %20f\n", x, asinh(x), log( x + sqrt(x*x+1)));
```

This code produces the following output:

```   x          asinh(x)        log( x + sqrt(x*x+1))
-------------------------------------------------------
-2.00       -1.443635            -1.443635
-1.50       -1.194763            -1.194763
-1.00       -0.881374            -0.881374
-0.50       -0.481212            -0.481212
0.00        0.000000             0.000000
0.50        0.481212             0.481212
1.00        0.881374             0.881374
1.50        1.194763             1.194763
2.00        1.443635             1.443635
```