how do you find area of triangles

3 ways.

1) Let b denote the base of the triangle and h denote the height of the triangle.

Area = $\dfrac{bh}{2}$

2) Let a, b, c denote the 3 sides of the triangle respectively and s = $\dfrac{\text{Perimeter}}{2}$

Area = $\sqrt{s(s-a)(s-b)(s-c)}$

3) Let a and b denote any 2 sides of the triangle and $\theta$ denote the angle included in the 2 sides.

Area = $\dfrac{ab\sin \theta}{2}$

Where $\sin x = \dfrac{e^{ix}-e^{-ix}}{2i}$

Where $e^x = 1 + x + \dfrac{x^2}{2}+\dfrac{x^3}{2\times 3}+\dfrac{x^4}{2\times 3\times 4}+......$

and $i = \sqrt{-1}$