addition formula
Mathematics
noun
An equation in which one quantity is expressed in terms of a sum of other quantities; specifically any of several standard formulae which express a trigonometrical function of a sum or a difference of angles as a sum or difference of products of similar functions of the individual angles.
- An example of a trigonometrical addition formula is sin (A + B) = sin A cos B + cos A sin B..
Origin
Late 19th century; earliest use found in Proceedings of the Royal Society of London.