An angle which is greater than $180^{\circ}$ but less than $360^{\circ}$ is called a $\ldots \ldots \ldots .$.

Prove that the sum of the three angles of a triangle is $180^{\circ}$.

In $\Delta PQR$,$\angle P : \angle Q : \angle R = 5 : 2 : 2$. Find the measure of each angle of $\Delta PQR$.

In the figure,$OD$ is the bisector of $\angle AOC$,$OE$ is the bisector of $\angle BOC$,and $OD \perp OE$. Show that the points $A, O$,and $B$ are collinear.

The sum of a linear pair of angles is always.......... (in $^{\circ}$)

State whether each of the following statements is true or false:
$(1)$ The maximum number of right angles in any triangle is two.
$(2)$ The supplementary angle of the complementary angle of an angle having measure $33^{\circ}$ has measure $123^{\circ}$.