  Trigonometry is one of the topics in mathematics that the students in both
high school and pre-undergraduate levels need to learn. Generally, the topic
covers trigonometric functions, trigonometric equations, trigonometric
identities and solving oblique triangles using the Laws of Sines and Cosines.
However, when solving the oblique triangles, Mollweide's formula is most likely
to be omitted from the discussion. Mollweide's formula--which exhibits a
cyclical nature--is particularly useful in checking one's result after solving
an oblique triangle since all six components of the triangle are involved. It
is interesting to note that proving Mollweide's formula can be performed
without words. Furthermore, the Law of Tangents can be derived
straightforwardly from this equation. In this article, we revisit Mollweide's
formula and provide classroom examples where this equation comes into alive. In
addition, we suggest that this seemingly less-known equation is to be included
in the mathematics syllabus on the topic of Trigonometry.
