Getting the error of inner dimensions must agree

Below is the code for which I am getting the error

deltapsi=(-40:5:30)

deltathi=(9*(deltapsi.^2))/(8*3.142);

p=1

S=sin(deltathi-deltapsi)-(p*sin(deltapsi)*sin(deltathi));

The error is

Error using  * 
Inner matrix dimensions must agree.

Error in Untitled (line 4)

S=sin(deltathi-deltapsi)-(p*sin(deltapsi)*sin(deltathi));

I need to plot S versus deltapsi

Answer 1

[Walter Roberson]

Use .* instead of *

Answer 2

[Abdullah Nasir]

Thank you for the help Can I know the explanation where was I wrong

[Walter Roberson]

The .* operator is formally called times and multiplies corresponding elements in two arrays that are the same size. It can be used for arrays of more than 2 dimensions. https://www.mathworks.com/help/matlab/ref/times.html

The * operator that you used is formally called mtimes, and is algebraic matrix multiplication. The two arrays it multiplies are not generally the same size, but must be 2D, and the number of columns of the first array must equal the number of rows of the second array -- P x N * N x Q giving P x Q. https://www.mathworks.com/help/matlab/ref/mtimes.html