Since it is a square you can use the Pythagorean theorem (a²+b²=c²) by filling in what you know. a²=5 and b²=5 so you have 5²+5²=c². This simplfies to 25+25=c². Now you simplify again to get 50=c². Finally you have to square root everything because the equation can't end in c², it has to be the most simplified it can be. This equals ≈7.1