**ERIC Number:**EJ926151

**Record Type:**Journal

**Publication Date:**2011-Jun

**Pages:**5

**Abstractor:**As Provided

**ISBN:**N/A

**ISSN:**ISSN-0268-3679

Mollweide's Formula in Teaching Trigonometry

Karjanto, Natanael

Teaching Mathematics and Its Applications: An International Journal of the IMA, v30 n2 p70-74 Jun 2011

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.

Descriptors: Mathematics Activities, Geometric Concepts, Trigonometry, Mathematics Instruction, Mathematics Education, Mathematics, Mathematical Concepts, Equations (Mathematics), Higher Education, Mathematical Formulas, Course Descriptions

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**Publication Type:**Journal Articles; Reports - Descriptive

**Education Level:**N/A

**Audience:**Teachers

**Language:**English

**Sponsor:**N/A

**Authoring Institution:**N/A