https://www.khanacademy.org/math/geometry
https://www.khanacademy.org/math/geometry/intro_euclid
https://www.khanacademy.org/math/geometry/parallel-and-perpendicular-lines
https://www.khanacademy.org/math/geometry/congruent-triangles
https://www.khanacademy.org/math/geometry/similarity
https://www.khanacademy.org/math/geometry/right_triangles_topic
https://www.khanacademy.org/math/geometry/basic-geometry
https://www.khanacademy.org/math/geometry/cc-geometry-circles
https://www.khanacademy.org/math/geometry/triangle-properties
https://www.khanacademy.org/math/geometry/quadrilaterals-and-polygons
https://www.khanacademy.org/math/geometry/transformations
https://www.khanacademy.org/math/geometry/analytic-geometry-topic
https://www.khanacademy.org/math/geometry/geometric-constructions
https://www.khanacademy.org/math/geometry/geometry-worked-examples