Hello Jason,
"(1-cos(t))i" means that this point will be at the x-coordinate "1-cos(t)" for time t. Similarly for "j" -> y-coordinate. So you're on the right track, but the trick is to know that MATLAB doesn't care what time it is while plotting. It only wants to know the x and y coordinates.
t = linspace(-1, 1, 10);
x = 1 - cos(t);
y = 1 + 2*t + t.^2;
plot(x, y)
The error was likely because you were defining "x" instead of "t" in the first line, but you had an existing "t" value left over from before. Be careful about that when writing scripts.
Also, I'd recommend against using "i" or "j" as variable names in MATLAB, since they have a built-in meaning as the imaginary unit.
-Cam
