TANH()

Syntax. TANH(number)

Definition. This function returns the hyperbolic tangent of a number.

Argument

  • number (required) Any real number

Background. The hyperbolic tangent belongs to the hyperbolic functions, which are (like the circle functions) defined for all real and complex numbers. (However, Excel allows only real arguments, not complex arguments, for hyperbolic functions.)

The formula for the hyperbolic tangent is:

image with no caption

The last term shows the similarity with the trigonometry functions.

The hyperbolic tangent is often used for research and development in engineering and natural sciences (see Figure 16-40).

The hyperbolic tangent.

Figure 16-40. The hyperbolic tangent.

You might miss the corresponding cotangent you know from the trigonometry functions: sin, cos, tan, and cot. However, neither the trigonometric cotangent nor the hyperbolic cotangent is implemented as a table function, because cotangent = tangent–1:

  • Cotangent:

    image with no caption
  • Hyperbolic cotangent:

    image with no caption

From this, it follows that the hyperbolic cotangent is:

image with no caption

Instead of

=COTH(A1)

(COTH doesn’t exist), enter

=1/TANH(A1)

Example. The hyperbolic tangent is used to calculate the propagation speed of waves. The formula for the propagation speed υ of waves is:

image with no caption

This formula uses the gravity acceleration g [m/s2], wave length λ [m], and water depth h [m].

If you enter this formula into a table, you can use the following two approximate formulas for shallow and deep water:

  • Shallow water:

    image with no caption
  • Deep water:

    image with no caption

More examples of this function are:

  • =TANH(0) returns 0.

  • =TANH(1) returns 0.761594156.

  • =TANH(-1) returns -0.76159416.

  • =TANH(10) returns 1.

  • =TANH(-10) returns -1.

See Also

ACOSH(), ASIN(), ATANH(), COSH(), SINH()

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