Category Archives: Geometry

Hyperbolas Covered by a Quadrilateral

Four points $A$, $B$, $C$ and $D$ are chosen on each of $4$ hyperbola branches of $x^2y^2=1$ (as $y=\dfrac{1}{x}$ and $y=-\dfrac{1}{x}$ combined). Find the minimum area of the quadrilateral.🔑 Solution: Given that all 4 vertices of the quadrilaterial are on the $4$ branches, let … Continue reading

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Hyperbolas Covered by a Triangle

$x^2y^2=1$ forms $4$ hyperbola branches, as $y=\dfrac{1}{x}$ and $y=-\dfrac{1}{x}$ combined. What is the smallest triangle in terms of area that it intersects all $4$ branches.🔑 Solution: Obviously, to be the smallest triangle, the vertices of the triangle must be on … Continue reading

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Geometry Challenge – 2025/06/07

Two opposite edges of a unit square are folded along one of the diagonal to form a parallelogram. Then, those two opposite edges on the parallelogram are folded together to form a trapezoid. Find the area of the trapezoid.🔑 Solution: … Continue reading

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Geometry Challenge – 18

Two squares $ABCD$ and $DEFG$ are inscribed inside a unit semi-circle, as shown in the following diagram, with $CD$ and $DE$ on the same line, $A$, $D$, $G$ on the diameter of the semi-circle, and $B$ and $F$ on the … Continue reading

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Geometry Probability – 4

Let $D$ is an interior point inside equilateral $\triangle{ABC}$. Find the probability that the line segments of $AD$, $BD$, and $CD$ are the side of: (1) a triangle, (2) a right triangle, (3) an obtuse triangle, and (4) an acute … Continue reading

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