Important for my exam tomorrow ! Please help

Step-by-step explanation:

Adjacent angles of parallelogram are supplementary.

∠A + ∠D = 180

Divide both sides by 2

∠A + ∠D = 90

∠PAD + ∠ADP = 90       --------------------(I)

IN ΔPAD,

∠PAD + ∠ADP + ∠APD = 180 {angle sum property of triangle}

90  + ∠APD = 180         {from (I)}

          ∠APD = 180 - 90

         ∠APD = 90

∠SPQ = ∠APD             {vertically opposite angles}

∠SPQ = 90°

Similarly, we can prove ∠PQR = 90° ; ∠QRS = 90° and ∠RSP = 90°

In a quadrilateral if each angle is 90°, then it is a rectangle.

PQRS is a rectangle.