Two circles, one having its centre on the other, and four line segments. Prove that the three coloured line segments are congruent.
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Two circles, one having its centre on the other, and four line segments. Prove that the three coloured line segments are congruent.
Four orange unit circles and their red centres. What is the radius of the green circle? Kindly provided by Marshall W. Buck.
Two triangles and an extended side. What’s blue : orange?
A circle with an inscribed quadrilateral. Prove that ab=cd. Kindly provided by Marshall W. Buck.
A circle with two tangents. What’s red : blue in terms of α?
A triangle with a cevian. What’s α?
Two lines connected by five triangles. Prove that orange = blue. Created by Marshall W. Buck.
A triangle with two angular bisectors. What’s the proportion blue : red?
Two equilateral triangles and one centre. What’s green : red?
An arbitrary point on the parabola y=x2. Shown are the tangent in that point and a line segment perpendicular to it. What is the minimal height h?