MATLAB: How to solve numerical derivation

I am a beginner of matlab. I solved my problem using mathcad but also want to try it using matlab so it would be nice if anyone could assist me with some basic idea for solving this problem.
This is the figure that i solved in mathcad with all the given data.

Best Answer

If you want to evaluate dC(x)/dx, you have to have the Symbolic Math Toolbox:
syms x
a = 0.1;
b = 0.3;
l = 0.25;
e = 71E-11;
C(x) = (2*pi*e*l)./acosh((a.^2 + b.^2 - x.^2)./(2*a*b));
dC = diff(C,x);
x = 0.05;
dCx = vpa(dC(x), 5)
dCx =
1.2753e-9
The vpa function limits the number of digits the numerical result is displayed with, and converts fractions that might otherwise result from the derivation to decimals.
The Symbolic Math Toolbox is an add-on (not part of core MATLAB), but worth buying if you do relatively frequent symbolic calculations.
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