$$A = l \times w $$

- _A_: Area

- _l_: Length

- _w_: Width

Triangle

$$A = \frac{1}{2} \times b \times h$$

- _A_: Area

- _b_: Base

- _h_: Height

Circle

$$A = \pi r^2$$

- _A_: Area

- _r_: Radius