The equation cosh(-x) = cosh(x) illustrates a property of the hyperbolic cosine function, which is defined as cosh(x) = (e^x + e^(-x)) / 2. This function is even, meaning it produces the same output for both positive and negative inputs. This symmetry can be understood by substituting -x into the definition of cosh(x). When you do this, the terms involving e^(-x) and e^x remain unchanged, confirming that cosh(-x) equals cosh(x). This property is useful in various fields, including mathematics and physics, where hyperbolic functions are applied.