Here you want to use the Pythagorean Theorem.
[tex] a^{2} + b^{2} = c^{2} [/tex]
Remember that the hypotenuse ( c ) will always be the longest side, opposite of our right angle.
let's enter in the numbers on the picture into our theorem.
[tex] 4^{2} + 1^{2} = c^{2} [/tex]
now lets simplify
[tex] 4^{2} = 16 \\ 1^{2} = 1 \\ \\ 16 + 1 = c^2 \\ \\ 17 = c^2 \\ \\ \sqrt{17} =c[/tex]
and there you are! [tex] \sqrt{17} = c[/tex]
Hope this helped!:)
