Given circleR, how is it known that QS = YT
(idk the answer it was a guess)

The diameters acts as diagonals

Step-by-step explanation:

QTSY is known to be a rectangle inscribed successfully inside a circle.

Now one of the properties of a rectangle is that it's diagonal divide it's shape into two equal parts and that it's has two equal diagonals.

In this case, the diagonals are QS and YT.

Another thing to observe it's that the diagonals of the rectangle pass through the center of the circle R and touching the circumference at both ends making the both diagonals a diameter as well.

So to prove that QS=YT

they are both diagonals that are diameters and they are equal because diameters of a circle are always equal while diagonals of a rectangle are also always equal.