If the legs are equal to 4 cm and 5 cm, respectively we can rewrite the equation 42+52=c2 -> 16+25=41=c^2 so then, c= the square root of 41, which is an irrational number.
It's gonna be an irrational number because the length of the hypotenuse is 6.40312....... cm
An irrational number cannot be written as a simple fraction and the decimals would keep on going without a pattern (if it was repeating, it would be rational).
