Three circles with their centres and a triangle ABC. Given that D is the midpoint of BC, prove that quadrilateral ABEF and triangle ECF have both equal perimeter and equal area.
Two overlapping equilateral triangles with side lengths 1. What is the total red length?
A square is divided in two quadrilaterals of given area. What fraction of the square’s perimeter is red?
Two unit squares (having side 1) are placed as shown. What is the total perimeter of the two red triangles?