Post Number:#2 by dshasan » Fri Feb 03, 2017 11:57 am
$\text{Problem 8}$
Join $B,O$. In $\bigtriangleup ABO$ and $\bigtriangleup BOC$, $\angle COB = \angle ABO$ and
$\angle CBO = \angle AOB$ and $BO$ is the common side. So, $\bigtriangleup ABO$ is congruent to $\bigtriangleup BOC$. So, $\angle OAB = \angle OCB \Rightarrow \angle OAB = \angle CBO
\Rightarrow \angle OAB = \angle AOB$. Therefore, $\bigtriangleup ABO$ is equilateral and $\angle OAB = 60$.
The study of mathematics, like the Nile, begins in minuteness but ends in magnificence.
- Charles Caleb Colton