rectangular cartensian co-ordinates — MATHS STD 11 Science — Question

$\Rightarrow \angle \mathrm{ADP}+\angle \mathrm{DAP}=90^{\circ}$ (because $DQ$ and $AS$

are angle bisectors of angle $A$ and $ D$)

$\Rightarrow \angle \mathrm{DPA}=90^{\circ} \Rightarrow \angle \mathrm{SPQ}=90^{\circ} .$ Similiarly

$\angle \mathrm{PSR}=90^{\circ}, \quad \angle \mathrm{SRQ}=90^{\circ}, \quad \angle \mathrm{PQR}=90^{\circ} . \mathrm{So}$

$PQRS$ is a rectangle.