$(1)$ $A$ quadrilateral in which only one pair of opposite sides are parallel is a $\ldots \ldots \ldots$.
$(2)$ The diagonals of a rectangle are $\ldots \ldots \ldots$.

If bisectors of $\angle A$ and $\angle B$ of a quadrilateral $ABCD$ intersect each other at $P$,of $\angle B$ and $\angle C$ at $Q$,of $\angle C$ and $\angle D$ at $R$,and of $\angle D$ and $\angle A$ at $S$,then $PQRS$ is a

Diagonals of a rhombus are equal and perpendicular to each other. Is this statement true? Give reason for your answer.

In a parallelogram $ABCD$,$AB = 10 \, cm$ and $AD = 6 \, cm$. The bisector of $\angle A$ meets $DC$ in $E$. $AE$ and $BC$ produced meet at $F$. Find the length of $CF$ (in $cm$).

In $\Delta ABC$,$P$,$Q$,and $R$ are the midpoints of $AB$,$BC$,and $AC$ respectively. If $AB = 8 \text{ cm}$,$BC = 9 \text{ cm}$,and $AC = 10.6 \text{ cm}$,find the perimeter of $\Delta PQR$ in $\text{cm}$.

Diagonals of a parallelogram are perpendicular to each other. Is this statement true? Give reason for your answer.