The Story of the Youth Who Went Forth to Learn What Fear Was undressed yourself to teach us fear.." as in figuratively "put something on, you've put yourself out to teach fear."). The Story of the Youth Who Went Forth to Learn What Fear Was "The Story of the Youth Who Went Forth to Learn What Fear Was" or "The Story of a Boy Who Went Forth to Learn Fear" () is a German folktale collected by the Brothers Grimm. It is tale number 4 in the collection. It was also included by Andrew Lang in "The Blue Fairy Book" (1889). The Grimms' first, 1812 edition contained a much shorter version, "Good Bowling
Proof that π is irrational In 1761, Lambert proved that is irrational by first showing that this continued fraction expansion holds: Then Lambert proved that if "x" is non-zero and rational then this expression must be irrational. Since tan(/4) = 1, it follows that /4 is irrational and therefore that is irrational. A simplification of Lambert's proof is given below. This proof uses the characterization of as the smallest positive number whose half is a zero of the cosine function and it actually proves that is irrational. As in many proofs of irrationality, the argument proceeds by reductio ad absurdum. Consider the sequences ("A") and