Julia Kagan is a financial/consumer journalist and former senior editor, personal finance, of Investopedia. Vikki Velasquez is a researcher and writer who has managed, coordinated, and directed ...

A triangle is a polygon. It is a closed 3-sided shape made up of straight lines. The ‘tri-’ part of the word triangle means three. A triangle has 3 sides and 3 angles. Interior angles are the angles ...