The expression e^x + e^-x is a mathematical function that combines two exponential terms. Here, e is the base of natural logarithms, approximately equal to 2.718. The term e^x represents exponential growth, while e^-x represents exponential decay. Together, they create a symmetric function around the y-axis. This expression is closely related to the hyperbolic cosine function, denoted as \cosh(x) . Specifically, \cosh(x) = \frace^x + e^{-x}2 . This relationship highlights how e^x + e^-x can be used to describe various mathematical and physical phenomena, including waveforms and growth patterns.