Trigonometric functions, in particular the sine and cosine functions, play a relevant role in physics and various branches of mathematics. In view of their importance the properties of these functions have been studied intensively. Of special interest are inequalities for trigonometric functions. In his classical book Analytic Inequalities D.S. Mitrinovic dedicated a whole section to this subject. In the recent past, several authors discovered remarkable new inequalities for sine, cosine, and their relatives. Many of them appeared in the Journal of Inequalities in Pure and Applied Mathematics, in Mathematical Inequalities and Applications, and in the Journal of Inequalities and Applications.