So in physical science i'm learning about vectors using the pythagoream theorem, and when i get what c equal i wanted to know if i round to the next highest number, put it is a decimal, or do nothing at all. Helppp pleaeee[:

It depends on the problem.

If the two orthogonal components (at right angles) are given to 4 significant figures, your answer should do the same.
For example,
x=42.34
y=55.31
z=√(x²+y²)
=(69.65578)
But 69.65578 has 7 significant figures, which is more than the original information, so round to the same number of figures, namely 69.66 would do.