Can someone explain to me how to code the Tangent line and Normal line

[Davide Masiello]

Your code seems to be correct, what is the problem?

[Echo Lei]

Answer 1

[Torsten]

https://de.mathworks.com/matlabcentral/answers/1816450-can-someone-tell-me-how-will-i-be-able-to-remove-the-error-in-this-script-i-have-already-the-answer?s_tid=srchtitle

[Echo Lei]

Thank you very much!

Answer 2

[Davide Masiello]

syms x m b yt

f(x) = 3^x+3*x+2;                       % Function
m    = diff(f,x)                        % Slope of tangent line

m(x) = 

b       = f-m*x;                        % Intercept of tangent line
x0      = randi([-5 5]);                % Random point x
b       = subs(f,x0)-subs(m,x0)*x0;     % Intercept value at random point                                 % Redefine x as symbolic variable
yt(x)   = subs(m,x0)*x+b                % Tangent line equation at random point

yt(x) = 

fplot(x,f(x))                           % Plot function
hold on
fplot(x,yt(x),'r')                      % Plot tangent
plot(x0,subs(yt,x0),'ok')               % Plot point of tangency

You can use the same procedure for the normal line.