error message: Form of equation?

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!

Answer 1

[Roger Stafford]

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);

[Joseph]

That was it! Thank You!