5.7 | Law of Cosines


Law of Cosines:
$$
\begin{aligned}
a^2 & = b^2 + c^2 -2bc \cos A \\
b^2 & = a^2 + c^2 -2ac \cos B \\
c^2 & = a^2 + b^2 – 2ab \cos C
\end{aligned}
$$
Heron’s Area Formula: Given any triangle with sides of length \(a,b,\) and \(c,\) the area of the triangle is
$$
\text{Area} = \sqrt{s(s-a)(s-b)(s-c)}
$$
where \(s = (a+b+c)/2.\)

E 5.7 Exercises