A trapezium containing three right angles is split in two. What is the proportion of the areas yellow : blue?

# Month: April 2021

## The fallen pine

Two congruent isosceles triangles and three lines. Prove triangle AEF is also isosceles.

## The color fan

Two congruent rectangles share a vertex. Given that the three coloured areas are equal, what is the width x?

## The right angle

Two triangles inside a quarter circle. What is their area proportion?

## The triangle quartet

A square is divided into four triangles. The red area equals the blue area. What is the angle α?

## The corner stone

Four squares inside another square. What fraction is yellow?

## The bigger picture

In a small square two perpendicular lines are drawn. A larger parallel square is constructed as shown. Prove it is a scaled copy of the smaller square but rotated 90° anticlockwise.

## La Flèche Wallonne

A triangle is divided in four. What is the black area?

A rectangle of height 2 is crossed by two line segments at right angles. What is its width?

## The navel orange

Two quarter circles and a semicircle inside a circle. What fraction of the circle is shaded by the semicircle?