A parallelogram and four equilateral triangles. What is yellow : green?
A pink parallelogram with two extended sides. What’s α : β?
Four equilateral triangles. Prove that the red quadrilateral is a parallelogram.
Two ellipses go through each others focal points. Prove that the focal points are the vertices of a parallelogram.
Three parallelograms are inscribed in a circle. Prove that the common red vertex is the orthocentre of the dashed triangle.
A parallelogram ABCD with a circle and a diameter CE. Prove that point E is the orthocentre of triangle ABD.
A parallelogram is divided into several areas. What is the area X of the blue trapezium?
An equilateral triangle containing a parallelogram, another equilateral triangle and a circular arc that is tangent in its base vertices. What is the proportion pink : blue?
A large triangle with one side tangent to a circle. The tangency point is the vertex of a blue parallelogram. What is the red area?
Three squares and three shared vertices. Prove that the orange quadrilateral is in fact a parallelogram.