Categories
Intermediate

The tin foil hat

A circle inside a quarter circle. The triangle connects the two tangency points and the top of the quarter circle. What’s the angle α?

Categories
Intermediate

Lazy Friday

Four congruent squares plus another one. What is the angle α?

Categories
Advanced

Tympanum II

A regular pentagon with a diagonal. What is the top angle of the isosceles triangle?

Categories
Beginner

The pillbox

Three touching circles in a rectangle and a common tangent. What’s the angle?

Categories
Advanced

The tympanum

A regular pentagon with a diagonal and an extended side. What is the top angle of the isosceles triangle?

Categories
Beginner

The winged messenger

A semicircle and two quarter circles pass through the same point. What’s the angle α?

Categories
Beginner

The seventies tipi

An isosceles triangle with two inscribed congruent semicircles. What is the angle α?

Categories
Intermediate

The right angle

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

Categories
Intermediate

The triangle quartet

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

Categories
Intermediate

The Chihuahua

A circle and a right triangle. What’s the angle α?