New posts in Quadrilateral

Area of a square inside a square created by connecting point-opposite midpoint

Calculating area of quadrilateral when distance of vertices from an arbitrary point is known

What is a simple (or not) way of finding the lengths of the diagonals of this rhombus?

Is every parallelogram a rectangle ??

Where do you see cyclic quadrilaterals in real life?

Does the square or the circle have the greater perimeter? A surprisingly hard problem for high schoolers

Maximum area of a square in a triangle

Trisect a quadrilateral into a $9$-grid; the middle has $1/9$ the area