In high school, you probably learned that trigonometric functions – like sine, cosine and tangent –can be derived, geometrically, from a circle (hence why trig functions are also known as “circular” ...

In support of efforts to foreground functions as central objects of study in algebra, this study provides evidence of how secondary students use trigonometric functions in contextual tasks. The author ...

Let X be a complex Banach spcce, and denote by T a strongly continuous semigroup of linear operators denned on X and C by a cosine function of operators with associated sine function S defined on X.