Category:Cosine of Half Angle in Triangle

This category contains pages concerning Cosine of Half Angle in Triangle:

Let $\triangle ABC$ be a triangle whose sides $a, b, c$ are such that $a$ is opposite $A$, $b$ is opposite $B$ and $c$ is opposite $C$.

Let $s$ denote the semiperimeter of $\triangle ABC$.

Then:

$\cos \dfrac C 2 = \sqrt {\dfrac {s \paren {s - c} } {a b} }$