GeoDom

En la figura, $P$, $Q$ y $T$ son puntos de tangencia. Encuentre la medida de $\angle{ATM}$. Lema 1 . Denotemos con $I$ el incentr...

Let $I$, $O$ and $\tau$ be the incenter, circumcenter and circumcircle of triangle $ABC$. The circle $\omega$ is tangent to lines $AB$ and ...

Let $I$, $O$ and $\tau$ be the incenter, circumcenter and circumcircle of triangle $ABC$. The line $BI$ intersects $\tau$ again at $M$. The...

Let $E$ be the center of the square $ABCD$. Call $F$ the midpoint of $AE$ and let $DF$ meet $AB$ in $H$. Then, $AH=\frac{AB}{3}$. P...

For a description and proof click  here .

Considera tres cuadrados, $ABCD$, $DPEF$ y $PBGH$, dispuestos como se muestra en la animación. Demostrar que $F$, $C$ y $G$ están aline...

Laurent Schwartz, as quoted from   A Mathematician Grappling with His Century,  Birkhäuser Basel, 2001, pp. 30-31. [With thanks to Jonathan...