Define incentre of a triangle.

In the above figure, $AD, BE$ and $CF$ are the altitudes of the $△ABC$ and they meet at the point $O$. Therefore, $O$ is 

Match each term with the correct definition:

In the above figure, $AD, BE$ and $CF$ are the interior angle bisectors of the $△ABC$ and they meet at the point $O$. Therefore, $O$ is the 

Altitudes of a triangle meet at a point. The point is called _____.

The bisectors of angles $\mathrm{A}$ and $\mathrm{B}$ of a scalene triangle $\mathrm{ABC}$ meet at $\mathrm{O}.$

$\mathrm{OR}$ and $\mathrm{OQ}$ are drawn perpendiculars to $\mathrm{AB}$ and $\mathrm{CA}$ respectively. What is the relation between $\mathrm{OR}$ and $\mathrm{OQ} ?$

The bisectors of angles $\mathrm{P}$ and $\mathrm{Q}$ of a scalene $△\mathrm{PQR}$ meet at $\mathrm{O}$. What is the relation between angle $\mathrm{PRO}$ and angle $\mathrm{QRO}$?

Match each term with the correct definition:

Perpendicular bisectors of the sides $\mathrm{AB}$ and $\mathrm{AC}$ of a triangle $\mathrm{ABC}$ meet at $\mathrm{O}$. What do you call the point $\mathrm{O}$?