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 ...

The Mathematics Teacher (MT), an official journal of the National Council of Teachers of Mathematics, is devoted to improving mathematics instruction from grade 8-14 and supporting teacher education ...

However, it's still hard to get an intuitive sense of the relationship between the circle and the trigonometric functions and the triangles. That all changes with animated GIFs.