Titu Andreescu Geometry.pdf Now

Spiral similarities (a rotation + scaling) are a recurring nightmare for novices. This PDF breaks down how to find the center of a spiral similarity that sends one segment to another.

A transformative technique. The PDF teaches you when to invert (e.g., when you see multiple circles tangent to each other or lines through a point) and which radius to choose. Titu Andreescu Geometry.pdf

Not just "prove equal," but "prove less than." Problems involving Erdős–Mordell inequality, Euler's inequality, and Weitzenböck's inequality are solved with geometric finesse. Spiral similarities (a rotation + scaling) are a