Guest Post: Calculating Trignometric Values
Many students who start to learn Trigonometry often ask themselves how do we come to know that
or for that matter any other trigonometric value?
Most of us would say use a trigonometric table or use a scientific calculator and you get the value. That’s okay, but the question still remains unanswered. How does a calculator come to know that 
This rational approximate formula was discovered by Bhaskara I of India in the seventh century. This simple formula enables us to calculate the sine of any given acute angle (any even obtuse angle) with a maximum absolute error of 0.00163. » Read more
(link goes to Amazon) by Professor Richard Hammack, and so far, it was the best book that I have read about introduction to mathematical proofs. I recommend this book to high school students who are interested in pursuing a mathematics degree, to college students who are math majors, and to teachers who will teach or who are teaching an introductory course on mathematical proofs. Here are some of the reasons why I really like this book.