# How do I multiply a given function handle with the independent variable?

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Saurabh Madankar on 3 Apr 2023
Answered: Steven Lord on 3 Apr 2023
I have pre-defined n number of function handles f_{i} which are functions of t for i = 1 to n. How do I define a new function g_{i} = t.f_{i} and then evaluate the integral of each g_{i} from t=0 to 1?
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### Accepted Answer

Steven Lord on 3 Apr 2023
f = @sin;
g = @(t) t.*f(t);
format longg
[3*sin(3); g(3)] % Spot check by evaluating the function at t = 3
ans = 2×1
0.423360024179602 0.423360024179602
Now you can use g like any other function handle in functions like integral.
numericAnswer = integral(g, 0, 2*pi)
numericAnswer =
-6.28318530717959
syms x
symbolicAnswer = int(x.*sin(x), 0, 2*pi) % or
symbolicAnswer =
symbolicAnswer = int(g(x), 0, 2*pi)
symbolicAnswer =
[numericAnswer; double(symbolicAnswer)]
ans = 2×1
-6.28318530717959 -6.28318530717959
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### More Answers (1)

Use symfun and int in Symbolic Math Toolbox if you want to do integrals.
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