Can someone explain what's wrong with my formula?

Question

Kevin 2021-9-30

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评论： Kevin 2021-9-30

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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Answer 1

Matt J 2021-9-30

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编辑：Matt J 2021-9-30

在 MATLAB Online 中打开

Be careful of missing dots...

V = (-I./omega.*C).*cos(omega.*t)

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Kevin 2021-9-30

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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Answer 2

Walter Roberson 2021-9-30

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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 *