How can I change the code to get a tangent in the graph

syms x y
f(x)=-(sin(x/2)); % Input the function and interval 
Df=diff(f,x);
T(x)=Df*(x) 
disp('Tangent lines of f(x) at origin');
disp(T(x));
fplot(f(x)); 
legend(T(x),'tangent');
grid on;
hold on;
xlabel('x'); ylabel('y');
title('Graph of the tangent line');

Answer 1

[Ameer Hamza]

Compare following code with your code to see the mistakes

syms x y
f(x)=-(sin(x/2)); % Input the function and interval 
Df=diff(f,x);
T(x)=subs(Df,x,0)*x;
disp('Tangent lines of f(x) at origin');
disp(T(x));
fplot(f(x));
hold on
fplot(T(x))
legend({'curve', 'tangent'});
grid on;
xlabel('x'); ylabel('y');
title('Graph of the tangent line');

[Shreesh Sahai]

Can I write a similar code if there's not a function, but a graph is obtained from observed data points?

Or, is there a way to find the function of a graph which has random data points?