error message: Form of equation?

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Joseph 2014-9-2

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评论： Joseph 2014-9-2

I keep getting an error in the command window. Here is my equation and error message:

x = (1.2)*exp((-1/2)*t)*sin(3*t) + 5*exp((-1/2)*t)*cos(3*t);
Error using  * 
Inner matrix dimensions must agree.
Error in HW_3 (line 21)
x = (1.2)*exp((-1/2)*t)*sin(3*t) +
5*exp((-1/2)*t)*cos(3*t);

Thanks for any help!

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Answer 1

Roger Stafford 2014-9-2

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If t is an array, then to use matrix multiplication "*" the number of columns in exp((-1/2)*t) needs to be the same as the number of rows in sin(3*t). A similar statement hold for exp((-1/2)*t) and cos(3*t). Probably what you meant was:

x = (1.2)*exp((-1/2)*t).*sin(3*t) + 5*exp((-1/2)*t).*cos(3*t);