where am i going wrong? i get errors when i multiply the functions

Plot the following function from t=1 to t=2, sin(2*pi*3*t)*sin(2*pi*15*t). Label both axes, and give the plot a title. so this is the code i wrote but i keep get error. i am new at using matlab. I would like to know what i am doing wrong.

t= (1:1.1,2); x= sin(2*pi*3*t) y= sin(2*pi*15*t) c= (x*y)

Answer 1

[nl2605]

for t = 1:2

    x(t) = sin(2*pi*3*t);
    y(t) = sin(2*pi*15*t);
    c(t) = x(t).* y(t);
end

This should work

[nl2605]

You cannot just multiply two arrays or matrices like that.

http://www.mathworks.de/de/help/fixedpoint/array-and-matrix-operators.html

Follow this link for better understanding.

[Chris C]

The difference is the ".*" part when you multiply the two variables. The period tells matlab that you want to multiply each array element by the corresponding element in the other array instead of performing matrix multiplication.

[Emmanuel]

thanks. that was quite helpful the coresponding plot matches my manually generated graph.

Answer 2

[Joseph Cheng]

couple of things with your line.

1. for the t=1:1.1:2 are you attempting to get t=1 to 2 with increments of .1?if so it should look more like t=1:.1:2;
2. you should have a ";" after each function execution or atleast a "," to separate what you are doing. if you don't it will try to execute

t= (1:.1:2); x= sin(2*pi*3*t);y= sin(2*pi*15*t);c= (x.*y) as one single command.

3. the c = (x*y) will also give an error when it gets that far due to the matrix multiplication dimension mismatch. you'll have to use the element-by-element multiplication ".*". See element-by-element multiplication finally your line should look like

t= (1:.1:2); x= sin(2*pi*3*t);y= sin(2*pi*15*t);c= (x.*y)