A cyclic quadrilateral with its diagonals and two altitudes. Prove that AB is parallel to EF.
Two squares share a vertex. Three other vertices are collinear. What is the area proportion of the blue to the red square?
A square contains a right triangle. What fraction is orange?
Three tangent circles and a common tangent. The three tangency points are shown. What is α + β?
A triangle with a cevian. What is α?
A regular dodecagon and a square share two vertices. What is the area proportion square : dodecagon?
An isosceles trapezium with its inscribed circle. If the lengths are such that b-a=c-b=d-c, what is a : b : c : d?
A rectangle is divided into four similar triangles. What fraction is blue?
Four rectangles. The green and red rectangle are similar. What’s the area proportion of the orange and the blue rectangle?
Two ellipses go through each others focal points. Prove that the focal points are the vertices of a parallelogram.