The two short sides must be longer than those required in an isosceles right triangle. The ratio of side length to hypotenuse length in a 45°-45°-90° triangle is 1 : √2. So, such a triangle requires side lengths of 30/√2 ≈ 21.213 inches. Its perimeter will be about
... (30 +21.213 +21.213) in = 72.426 in
Since the perimeter needs to be slightly longer than that for the triangle to be acute, the smallest possible perimeter is ...
... 72.43 in
