Skip to content / Đến nội dung
ThichHocToan.com

MathNet 2023-part-05 — 191 problems (EN–VI) Question 33

Math Olympiad Vault · MathNet 2023-part-05 — 191 problems (EN–VI)

Question 33

Let $SABCD$ be a pyramid with the apex $S$ and whose base $ABCD$ is a parallelogram. We consider the points $M$, $N$, $P$ and $Q$ on the edges $SA$, $SB$, $SC$ and $SD$, respectively, such that $MNPQ$ is also a parallelogram.

a) If $ABCD$ is a rhombus, prove that $MNPQ$ is also a rhombus.

b) If $ABCD$ is a rectangle, prove that $MNPQ$ is also a rectangle.