Grades 9–10 · Geometry

📐 Geometry

Points, lines, angles, triangles, circles, and coordinate geometry — the visual logic of mathematics built step by step.

📐 10 Lessons ⏱ ~35 min each 💚 Always Free

Points, Lines, and Angles

Geometry begins with the simplest building blocks: points, lines, rays, and segments — then angles formed when lines mee...

Parallel Lines and Transversals

When a transversal crosses parallel lines, special angle pairs are formed — alternate interior, corresponding, and co-in...

Triangles: Angles and Sides

Triangles are the most fundamental polygon. The angle sum, triangle inequality, and special triangle types form the foun...

Triangle Congruence and Similarity

Two triangles can be proven congruent (same size and shape) or similar (same shape, proportional sides) using specific p...

The Pythagorean Theorem

In any right triangle, the square of the hypotenuse equals the sum of the squares of the two legs. This single theorem c...

Quadrilaterals and Polygons

Quadrilaterals have 4 sides and angle sum 360°. Each special type — parallelogram, rectangle, rhombus, square, trapezoid...

Circles: Arcs, Chords, and Angles

Circles have a rich set of relationships between central angles, inscribed angles, chords, tangents, and arcs....

Area, Surface Area, and Volume

Geometry extends to 3D: surface area measures the outer wrapping; volume measures the space inside. Each shape has disti...

Coordinate Geometry

Algebra and geometry merge on the coordinate plane. Distance, midpoint, slope, and equations of lines let us prove geome...

Transformations and Intro to Trigonometry

Transformations move or resize figures. Trigonometry extends the Pythagorean theorem to find sides and angles in any rig...