I plotted a graph of 2 straight lines with an intersection point using Matlab.
How to label the intersection point?
Is there any built-in function?
Not sure if there is a builtin function to do this, but depending on how complicated your functions are you might be able to use a code like:
MATLAB Central - File detail - Fast and Robust Curve Intersections
and use the matlab "text" function to label the points.