Given a triangle with sides $$a, b$$ and $$c$$ Heron's formula is:

$$A=\sqrt{p \cdot (p-a) \cdot (p-b) \cdot (p-c)} $$

where $$p$$ is the semiperimeter:

$$p= \dfrac{a+b+c}{2}$$

It works when all the sides of a triangle are known we can calculate the area with no need to know the height.