Categories
Intermediate

Velocipede III

Two tangent circles and two line segments of given length crossing at right angles at the tangency point. One of the line segments is parallel to a common tangent. What’s the total area?

Categories
Advanced

The rolling stones

If you roll a circle down a parabola, small circles can roll all the way down and up, whereas large circles get stuck between the sides at some point. What is the transition radius? In other words, what’s the maximum circle that keeps on rolling?

Categories
Beginner

The end of the tunnel

Two semicircles and two congruent triangles with a side of length 2. What’s the brown area?

Categories
Advanced

The rocking cradle

A semicircle and an interior circle are tangent to each other. The chord towards the tangency point is divided in segments of length 1 and 2. What is the pink area?

Categories
Intermediate

Caught in the middle

Two circles support a triangle. Prove it is equilateral.

Categories
Beginner

The monk’s hood

Two similar triangles inside a semicircle. What’s the angle?

Categories
Intermediate

Mars rover has landed

Two semicircles and two right triangles. What fraction of the large triangle does the small one cover?

Categories
Beginner

The observatory dome

A semicircle with a radius, a chord and an altitude. What is the angle?

Categories
Advanced

The PowerPoint

A point lies 8 from the centre of a circle of radius 6. The angle α is variable. What’s the maximum triangle area?

Categories
Intermediate

The toucan

Two congruent right triangles inscribed in a circle. The circle centre lies on one of the hypotenuses. What’s the angle?