I believe you have to use the Pythagorean Theorem. Which is a^2+b^2=c^2. Let’s say that 4=a, b=10, and c=hypotenuse(h)=x. We can use that information and plug it in. 4^2+10^2=x^2 = 16+100=x^2 = 116=x^2, then you find the square root of 116. You can simplify the square roof of 116 to 2 times the quads root of 29 if you wanted to keep it in radical form, or you could round to the nearest tenth for 10.8