Categories
Intermediate

Above the line

A triangle cut by a line and four parallel line segments. Prove that green = red.

Categories
Intermediate

Unity

A square, a rectangle and two semicircles, one of which is centered in the shared vertex. What is yellow : blue?

Categories
Intermediate

The Gakopoulos proportion

Two concentric quarter circles and a square. What is purple : red?

Categories
Intermediate

Egg of Columbus

An ellipse with its focal points, major and minor axis. What is x, the distance from the centre to the right focal point?

Categories
Intermediate

The Roman katapult

Two quarter circles and a circle with a tangent line segment. What is pink : green?

Categories
Advanced

Ice cream cone III

A triangle with its incircle and a cevian. What is red : yellow?

Categories
Intermediate

Slip sliding

Two squares share a vertex. The shown vertex can lie anywhere on the lower side. What is the maximum of red/blue?

Categories
Intermediate

Compartments

An equilateral triangle with a cevian and two inscribed circles. What is yellow : red?

Categories
Advanced

Crossing lengths

A cyclic quadrilateral (CDIF), where we form two segments: MK (green) with DM perp to FC and DK perp to FI; GJ (orange), with IG perp to FC and IJ perp to CD. What is the ratio MK:GJ ? What about MN:GN?

Categories
Intermediate

Lunar ratios

A circle of radius r is interior-tangent to the larger yellow circle of radius R, with diameters overlapping. Express s/k in terms of r and R.