I have troubles in understanding how could I turn some data type sym variables into data type symfun, can anybody make it clear for me?

% This program computes for the Tangent Line / Normal Line of a curve % about a given point
                   %define x for symbolic processing
syms x 
%IDENTIFY the function f(x)
f(x) = (4*x^2-2*x+1);

%DETERMINE the point of tangency (This will be a random point)
x0=randi([-5,5])
%SOLVE for the Ordinate of the point of tangency
y0=f(x0);  %Evaluate y given value fo x
y=73;
%FIND the slope function
yprime= diff(f,x)            %Solve for the first derivative
%Determine the slope at the given x0
m=yprime(x0); %sym(-42);         %Evaluate the slope
%Solve the equation of the tangent line
ytangent = -42*x+1/42
%Solve the Equation of the normal line
ynormal = 1/42*x+215/42

%DISPLAYING RESULTS
fprintf('The tangent line to f(x)=%s at (%.2f, %.2f) is y = %s \n',string(f(x)),x0,y0, string(ytangent))
fprintf('The normal line to f(x)=%s at (%.2f, %.2f) is y = %s \n',string(f(x)),x0,y0, string(ynormal))

%PLOTTING
g1=ezplot(f,[-15,15]);
set(g1,'color','b')
grid on
hold on
plot(x0,y0,'r*')
text(x0+1,y0,"Point of Tangency")
g2=ezplot(ytangent,[-15,15]);
text(5,5,["y(Tangent)=", string(ytangent)])
pause(1)
set(g2,'color','m')
pause(1)
g3=ezplot(ynormal,[-15,15]);
text(3,3,["y(Normal)=", string(ynormal)])
set(g3,'color','c');
title("Tangent Line and Normal Line")


Errors:
Variable m must be of data type symfun. It is currently of type sym. Check where the variable is assigned a value.
Variable ytangent must be of data type symfun. It is currently of type sym. Check where the variable is assigned a value.
Variable ynormal must be of data type symfun. It is currently of type sym. Check where the variable is assigned a value.

[Cris LaPierre]

What version of MATLAB are you using? There are no errors when running your code in R2023a.

% This program computes for the Tangent Line / Normal Line of a curve % about a given point
                   %define x for symbolic processing
syms x 
%IDENTIFY the function f(x)
f(x) = (4*x^2-2*x+1);

%DETERMINE the point of tangency (This will be a random point)
x0=randi([-5,5])

x0 = 4

%SOLVE for the Ordinate of the point of tangency
y0=f(x0);  %Evaluate y given value fo x
y=73;
%FIND the slope function
yprime= diff(f,x)            %Solve for the first derivative

yprime(x) = 

%Determine the slope at the given x0
m=yprime(x0); %sym(-42);         %Evaluate the slope
%Solve the equation of the tangent line
ytangent = -42*x+1/42

ytangent = 

%Solve the Equation of the normal line
ynormal = 1/42*x+215/42

ynormal = 

%DISPLAYING RESULTS
fprintf('The tangent line to f(x)=%s at (%.2f, %.2f) is y = %s \n',string(f(x)),x0,y0, string(ytangent))

The tangent line to f(x)=4*x^2 - 2*x + 1 at (4.00, 57.00) is y = 1/42 - 42*x 

fprintf('The normal line to f(x)=%s at (%.2f, %.2f) is y = %s \n',string(f(x)),x0,y0, string(ynormal))

The normal line to f(x)=4*x^2 - 2*x + 1 at (4.00, 57.00) is y = x/42 + 215/42 

%PLOTTING
g1=ezplot(f,[-15,15]);
set(g1,'color','b')
grid on
hold on
plot(x0,y0,'r*')
text(x0+1,y0,"Point of Tangency")
g2=ezplot(ytangent,[-15,15]);
text(5,5,["y(Tangent)=", string(ytangent)])
pause(1)
set(g2,'color','m')
pause(1)
g3=ezplot(ynormal,[-15,15]);
text(3,3,["y(Normal)=", string(ynormal)])
set(g3,'color','c');
title("Tangent Line and Normal Line")

[Girbaud]

Its the same but in my script it keeps saying I should change the variables into data type symfun because it is currently in data type sym.

[Cris LaPierre]

Where is it saying this? I'm not seeing it in 23a. What version of MATLAB are you using?

[Cris LaPierre]

Adding (x) will turn your sym variables into sym functions btw

syms x 
f(x) = (4*x^2-2*x+1);
yprime= diff(f,x);
x0=randi([-5,5]);
m(x)=yprime(x0);

whos m

  Name      Size            Bytes  Class     Attributes

  m         1x1                 8  symfun              

Answer 1

[Walter Roberson]

ytangent(x) = -42*x+1/42
%Solve the Equation of the normal line
ynormal(x) = 1/42*x+215/42