New posts in plane-geometry

Why does the Ellipsograph/Trammel of Archimedes draw an ellipse, really?

geometry conic-sections plane-geometry

What's the measure of the sid $BC$ in the quadrilateral below?

geometry euclidean-geometry plane-geometry

Why are the coefficients of the equation of a plane the normal vector of a plane?

calculus multivariable-calculus vectors plane-geometry

Conjecture about a point inside an equilateral triangle divided by integer angles

geometry number-theory trigonometry euclidean-geometry plane-geometry

Six points lie on a circle

geometry euclidean-geometry circles plane-geometry

Find the distance $ID$ in the triangle below

geometry euclidean-geometry plane-geometry

Does ONLY the ellipse have these properties?

conic-sections plane-geometry plane-curves affine-geometry

What's the measure of the segment $PD$ in the triangle below?

geometry euclidean-geometry plane-geometry

What's the measure of the segment $BD$ in the figure below?

geometry euclidean-geometry plane-geometry

What's the measure of the segment $PD$ in the pentagon below?

geometry euclidean-geometry plane-geometry

If $AB\parallel DC$, $BC\parallel AD$, and $AC\parallel DQ$, find $\Bbb X$ in terms of the areas $\Bbb A$, $\Bbb B$, and $\Bbb C$.

geometry euclidean-geometry area plane-geometry polygons

What's the measure of the segment HD in the pentagon below?

geometry euclidean-geometry plane-geometry

How many acute triangles can be formed by 100 points in a plane?

discrete-geometry extremal-combinatorics plane-geometry

What's the measure of the segment $PC$ in the pentagon below?

geometry euclidean-geometry plane-geometry

Does a line have 2 degrees of freedom or 1 degree of freedom?

linear-algebra geometry plane-geometry

What's the measure of the $\angle x$ in the figure below?

geometry euclidean-geometry plane-geometry

Configurations of eleven (or more) points in the Euclidean plane, such that out of any four there is a pair at unit distance.

graph-theory euclidean-geometry combinatorial-geometry plane-geometry

Regular polygons constructed inside regular polygons

geometry euclidean-geometry plane-geometry polygons discrete-geometry

Another chain of six circles

geometry euclidean-geometry plane-geometry

Accessible Proof of Denjoy-Riesz Theorem?

general-topology reference-request plane-geometry