help for MLE

From: Edward Sun

Dear Sir/Madam,

I am using R version 1.8.1. I am doing following tast:

First generate 100 Gaussion(3,1) numbers, then write the 
likelihood function 
to estimate the parameters of Gaussian distribution by direct 
maximizing the 
likelihood function.

My likelihood function is:

fn<-function(x) 
(-50*log((sd(x))^2))-50*log(sqrt(2*pi))-(1/2*((mean(x))^2))*(

sum((x-(mean(x))^2))

After I input above function, the '' >'' turned to be '' + 
''. and it did 
not work.

I am looking for the help to solve this tast by writting a likelihood 
function.

Thanks a lot.

Best regards.
edward sun