Categories
Intermediate

Above the line

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

Categories
Advanced

Kazakov triangles

A circle with its centre and three triangles consisting of chords and radii. Express area X in terms of A, B and α.

Categories
Beginner

Angle chase

Two triangles are placed as shown. What is the angle α?

Categories
Advanced

Ice cream cone III

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

Categories
Advanced

In and out II

A couloured triangle and rectangle with extended sides and two circles. Prove that the triangle and the rectangle have equal areas.

Categories
Intermediate

Side touches

Four triangles in a rectangle. The three red triangles have equal areas. What is blue : red?

Categories
Intermediate

Centre of attraction III

Three congruent squares and an equilateral triangle. What is blue : orange?

Categories
Intermediate

Compartments

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

Categories
Intermediate

The Grand Fir

A triangle, its circumcircle, circumcentre and two altitudes. What’s the angle α?

Categories
Advanced

The Simson split

A cyclic quadrilateral has side lengths a, c, j, and k. Three segments drop perpendicularly to two sides and one diagonal of the quad, forming the green and purple triangles between them. What is the ratio purple/green, in terms of a, c, j, k?