# Can someone explain what's wrong with my formula?

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Kevin il 30 Set 2021
Commentato: Kevin il 30 Set 2021
close all
clear
clc
syms t
omega = 2:2:6
omega = 1×3
2 4 6
I = 10
I = 10
C = 0.05
C = 0.0500
V = (-I./omega.*C)*cos(omega.*t)
Error using * (line 432)
Dimensions do not match.
fplot(V)
What is wrong with it? I get an error when I try to run it.
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### Risposta accettata

Matt J il 30 Set 2021
Modificato: Matt J il 30 Set 2021
Be careful of missing dots...
V = (-I./omega.*C).*cos(omega.*t)
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Kevin il 30 Set 2021
Sorry I'm still relatively new to using matlab, but thank you so much for taking your time to answer :D

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### Più risposte (1)

Walter Roberson il 30 Set 2021
omega is a vector, so (-I./omega.*C) is a vector and cos(omega.*t) is a vector the same size.
So you have 1 x 3 row vector * 1 x 3 row vector. But the * operator is algebraic matrix multiplication, "inner product". In the expresson A*B then size(A,2) must equal size(B,1) -- the "inner" dimensions must match. The first 1 x 3 vector operand for the * operation has 3 columns. The second 1 x 3 vector operand for the * operation has 1 row. But 1 is not equal to 3, so the * operation fails.
The element-by-element multiplication operator is .* instead of *
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