For this we will want to use the Pythagorean Theorem. Lets plug our values in.
5^2+4^2=c^2
Our first step is to find out our squared values.
25+16=^2.
You will then want to combine like terms.
41=c^2
Since C has a square, we will want to get rid of the squared. The opposite of squaring something is taking the square root of something.
We will then want to take the square root of 41.
Your final answer will be
C= 6.4