Composition of functions can be thought of as putting one function inside another. We use the notation {{MATH_18}} {{CMD_19}} The composition {{MATH_20}} only makes sense if {{MATH_21}} {{CMD_22}} In other words, the domain of a composite function {{MATH_23}} is the set of those inputs {{MATH_24}} in the domain of {{MATH_25}} for which {{MATH_26}} is in the domain of {{MATH_27}}.