# Formula for finding area for all polygons [duplicate]

I have a image below, kinda hard to see but was wondering if anyone has seen this formula and what its from and how to use it.

thx

$$A=\frac{1}{2}\sum\limits_{i=0}^{n-1}(x_iy_{i+1}-x_{i+1}y_i)$$

## marked as duplicate by David K, Strants, Xander Henderson, Jose Arnaldo Bebita-Dris, José Carlos SantosJul 19 '18 at 22:56

• The resolution of that image is terrible! In any case, you should never rely on images here when text/MathJax would suffice (except for specific geometric shapes to get ideas across). Visit this page for information on how to type with MathJax and $\LaTeX$ here. – JMoravitz Jul 19 '18 at 4:04