Checkmate patternsTriangle mate
Queen and rook team up with a contact check: the king, queen and rook form a triangle that leaves the enemy king nowhere to go.
How it works (spoiler)
The queen checks from the square diagonally next to the king, protected by the rook on the same rank. Together the queen and rooks cover every square around the king, so king, queen and rook form a triangle the king cannot escape — even in the middle of the board.