geometry formulas for area and perimeter of shapes

Triangle

circle area and perimeter formula
$$\textbf{Area of the triangle}$$
$$A = \frac{1}{2} h b$$
$$\textbf{or}$$
$$A = \sqrt{s (s - a) (s - b) (s - c)} ,$$
$$ s =\frac{a + b +c}{2}$$
$$\textbf{Perimeter of the triangle}$$
$$P = a + b + c$$