5144638
In a coordinate plane, points \(A(0, 0)\), \(B(w, 0)\), and \(C(w, h)\) form a right triangle with leg lengths \(w\) and \(h\). Use the Pythagorean theorem to analyze the hypotenuse length \(d\).
a) \(w = 1\) and \(h = 1\)
b) \(w = 3\) and \(h = 4\)
Based on these cases, evaluate the claim: “The diagonal of a square or rectangle with integer side lengths is never rational.”
Hints
- Use the Pythagorean theorem.
- When is the square root of a natural number rational?
- Look for familiar integer side-length combinations in right triangles.
Solution
1. For a), \(d = \sqrt{1^2 + 1^2} = \sqrt{2}\), which is irrational.
2. For b), \(d = \sqrt{3^2 + 4^2} = \sqrt{25} = 5\), which is rational.
3. Case b) is a counterexample to the claim because a rectangle with integer side lengths \(3\) and \(4\) has rational diagonal length \(5\). Therefore, the claim is false.
Answer
a) \(d = \sqrt{2}\), which is irrational.
b) \(d = 5\), which is rational.
The claim is false; a \(3\)-by-\(4\) rectangle has diagonal length \(5\).
