A real-valued function is a function whose range is contained in the real numbers. Thus it has the form
for some domain 
.
Real-Valued Function
See also
Complex Function, Function, Real Function, Real NumberExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Real-Valued Function." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/Real-ValuedFunction.html