The hapless frog and the evil wizard: an introduction to indirect proof
Vernon Thomas Sarver · Teaching Mathematics and its Applications An International Journal of the IMA · 2005
Students are introduced to indirect proof by a method of discovery. Initially, they are confronted with an intractable puzzle that they must either solve or expose as a hoax. Guided by timely clues, they are unwittingly led to discredit the puzzle by applying the strategy of indirect proof.