What is another word for parallelogram law?
Pronunciation: [pˌaɹəlˈɛləɡɹˌam lˈɔː] (IPA) 
The parallelogram law refers to a geometrical theorem, which states that the sum of the squares of the diagonals of a parallelogram is equal to twice the sum of the squares of its sides. This law is also known as the parallelogram identity, parallelogram formula, or parallelogram principle. In vector analysis, it is commonly referred to as the vector addition law, vector parallelogram law, or simply the parallelogram rule. This law is widely used in physics, engineering, and mathematics to calculate the resultant of two vectors acting simultaneously on an object. It is a fundamental concept that underpins much of modern geometry and vector calculus.
