// TOPIC // GEOMETRY
GEOMETRY
Triangles, circles, polygons, coordinate geometry, and a little trig — about a quarter of every paper.
What Geometry means on the AMC10
Geometry on the AMC10 rewards drawing carefully and seeing similar triangles. The recurring tools:
- Triangles — congruence, similarity, the Pythagorean theorem, special right triangles
- Circles — central and inscribed angles, power of a point, chords and tangents
- Polygons — interior angles, areas via decomposition
- Coordinate geometry — distance, slope, midpoint, intersections
- Three-dimensional figures — volume and surface area of prisms, pyramids, cones, cylinders, spheres
- Trigonometry basics — sine and cosine of common angles, the Law of Cosines when needed
If you find yourself doing heavy algebra on a geometry problem, stop and look for a similar-triangles shortcut. There almost always is one.