My first try (omitting chain of thought for brevity):
When you remove the cup and the mirror, you will see tails. Here's the breakdown:
Setup: The coin is inside an upside-down cup on a glass table. The cup blocks direct view of the coin from above and below (assuming the cup's base is opaque).
Mirror Observation: A mirror is slid under the glass table, reflecting the underside of the coin (the side touching the table). If the mirror shows heads, this means the underside of the coin is heads.
Coin Orientation: A coin has two sides: heads and tails. If the underside (facing the table) is heads, the top side (facing away from the table) must be tails.
Result: Removing the cup reveals the coin on the table. Since the top side was tails all along, you will see tails.
Key Insight: The mirror reveals the hidden underside of the coin, but the top side (visible after removing the cup) is its opposite. The mirror’s reflection does not alter the physical orientation of the coin’s sides—it simply reflects the existing state.
Answer: Tails.
