Gaussian filtering signal

[KlaussIT]

I would like to know how to properly filter a cosinus wave signal with a Gaussian Filter. I thought to use 'conv' to perform it. My code as follows :

s = cos(2*pi*f*t);
h = 1/(1/(sqrt(2*pi*var))*exp(-t.^2/2*var); %gauss filter
sF = conv(h,s,'same');

I used 'same' to keep the same length. Is it correct this method of filtering ? Another question, I heard about a parameter 'BT' (close to 0.5) for Gaussian Filter, how can I include it ? sigma = BT ?

Thanks for advance.

Best regards.