You are given a circle with a parallelogram inscribed in it.
You have to prove that the parallelogram is a rectangle.

How would you prove it?
Quote by seljer
if you draw a line through the centre of a circle and then choose another point on the rim, you always get a right triangle with 90° at the rim


But you cant state that a segment connecting the 2 supplementary points of the parallelogram will pass through the centerpoint.

I got something like:
- the two intercepted arcs cover the whole circle (is this given?)
- the two opposite angles are congruent and supplementary so it must be 90 degrees (what conjecture/ property is this?)
- consecutive angles of a parallelogram are supplementary (property of parallelogram)
- parallelogram is a rectangle