Sitting here angrily remembering the time I guessed that the distance between two randomly chosen points in a cube might be 1/√2, looked it up, and learned that it’s (1/105) × (4 + 17√2 - 6√3 + 21×ln(1 + √2) + 42×ln(2 + √3) - 7π) ≈ 0.661 and this was only worked out in 1978.