Learn geometry—angles, shapes, transformations, proofs, and more.

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Learn when to apply the reflexive property, transitive, and symmetric properties in geometric proofs. Learn the relationship between equal measures and congruent figures.

Prove theorems about lines and angles using triangle congruence criteria and algebra.

Let's carefully define translations, reflections, rotations, and dilations. What stays the same when we transform figures?

Learn high school geometry—transformations, congruence, similarity, trigonometry, analytic geometry, and more (aligned with Common Core standards).

Why are transformations useful in writing geometric proofs? We often use rigid transformations and dilations in geometric proofs because they preserve certain properties. Rigid transformations—such …

Quadrilaterals only have one side more than triangles, but this opens up an entire new world with a huge variety of quadrilateral types. Learn about it here.

Given a figure composed of 2 triangles, prove that the triangles are congruent or determine that there's not enough information to tell.

Learn what it means for two figures to be congruent, and how to determine whether two figures are congruent or not. Use this immensely important concept to prove various geometric theorems about …