A triangle with its excircles. The tangent radii are extended. Prove that the red line segments are concurrent and congruent.
Categories
Airbag ball
Tag: circle
Categories
Snow man scarf
Show that blue = red if and only if purple = orange.
Categories
Lemon slice II
A semicircle inscribed in a quarter circle. What fraction is yellow?
Categories
Cuckoo in the nest
Two tangent semicircles inscribed in another semicircle. What is the total area?
Categories
The tritium nucleus
Three discs are mutually tangent among themselves and with an enclosing circle of radius 18. The blue circle has radius 9. What it the common value of the radius of the gray discs?
Categories
The sundial
A circle with its centre and several line segments. The red one is a tangent. What is the angle α?
Categories
Cozy in his chair
Orange and green semicircles with equally long but perpendicular diameters (both length 2) are partially covered by a blue canopy at angle α. What is the orange area, which is not covered by either of the other regions, in terms of α?
Categories
The double iglo
Two semicircles with their centres. What’s the angle α?
Categories
Five tangents
Five points ABCDE are equally spaced around the dotted circle. A smaller red circle is tangent to (ABCDE) at a point F, between B and C. Blue and green tangents are drawn from ABCDE to the red circle, and are coloured blue and green as shown. Show that the length sum of the blue tangents equals the length sum of the green tangents.
Categories
Connected centres
Two quarter circles and a semicircle. The blue points are quarter and semicircle centres. What is red : green?