Returns the hyperbolic cosine of a complex number.

**Sample Usage**

IMCOSH(COMPLEX(4,1))

IMCOSH(C5)

IMCOSH("3+4i")

**Syntax**

IMCOSH(complex_number)

- complex_number - The complex number whose hyperbolic cosine is to be computed.

**Examples**

IMCOSH(COMPLEX(4,1)) returns the hyperbolic cosine of the complex number formed by the COMPLEX function.

IMCOSH(C5) returns the hyperbolic cosine of the complex number contained in C5.

**Notes**

- The IMCOSH function returns an error if the given number is not a valid complex number.
- complex_number can be either the result of the COMPLEX function, or a real number (interpreted as a complex number with imaginary part equal to 0), or a string in the format “x+yi” where x and y are numeric.