diff(x) question

[El Jeffo]

Gosh, the subscribe to this list was faster than I thought :)  
Perhaps you folks can help me out.

Say I have the following:

t=[1:.1:10]
x=sin(t)
and I want to plot the derivative of sin(t) (but I want to compute it)

I tried
y=diff(x)

and then plot(t,x,t,y) yields me an error message that states the
the vector sizes must be the same.. so I did
plot(t,x,[1.1:.1:10],y)

and it worked, but the y is really small and never goes beyond .1 in
value.  Do you think you could point me in the right direction?
I guess I'm differentiating wrong, how should this really be done?

Thanks :)

Jeff