Heron’s Formula:
This one isn’t always used but does come in extremely handy for computing the area of arbitrary triangles.
,
where 
and a, b, c are the lengths of the sides of the triangle.
In a picture it looks like:
Heron’s Formula:
This one isn’t always used but does come in extremely handy for computing the area of arbitrary triangles.
,
where
and a, b, c are the lengths of the sides of the triangle.
In a picture it looks like: