You have to define them numerically. Then, if you want to continue using the equation symbolically, use the subs function to replace them with their numeric equivalents. (Alternatively, define ‘xSol’ as a symbolic function of ‘C1’, ‘C2’, and ‘t’.)
If you want to use ‘xSol’ as an anonymous function to use elsewhere in your code, use the matlabFunction function to create it:
XFcn = matlabFunction(xSol)
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