Check for missing argument or incorrect argument data type in call to function 'integral'.

I have an issue with my function has an integral. I wish to integrate a function with one of my input variables defined for my function, but Matlab wants me to use syms to define the variable. I already change interagal to 'int' but it still dosent work. Is there a way I can work around this issue? Any help is appreciated and thank you for your time.

f = sqrt(2)*x^3;

a = integral(f, 0, 9);

syms theta sin

g = 4+2*(sin^2*(theta));

b = integral(g, 0, pi/2);

ans = a*b

Answer 1

[Voss]

syms x theta
f = sqrt(2)*x^3;
a = int(f, 0, 9)

a = 

g = 4+2*(sin(theta)^2);
b = int(g, 0, pi/2)

b = 

ans = a*b

ans = 

[AIMAN FATINA MUHAMAD KAMAL]

omg, thank you so much!

Answer 2

[Meg Noah]

One way is to use anonymous functions

f = @(x) sqrt(2)*x.^3;
g = @(theta) 4+2*(sin(theta).^2);
a = integral(f, 0, 9);
b = integral(g, 0, pi/2);
ans = a*b

[AIMAN FATINA MUHAMAD KAMAL]

thank you so much! both coding are same with my manual calculations.