https://www.khanacademy.org/math/geometry/hs-geo-circles/hs-geo-circle-basics/v/language-and-notation-of-the-circle 2021-02-16T16:08:13Z Circles glossary Formal definition of a circle. Tangent and secant lines. Diameters and radii. major and minor arcs Sal Khan video https://cdn.kastatic.org/googleusercontent/SWae14xdpXW141daSvXpqUJZzzdAUuYNQ8-Zz-oWkTnYjVHewnV66scU53oFOzvcpEBnymxptuVTkmroZudMhhyh Circles glossary Formal definition of a circle. Tangent and secant lines. Diameters and radii. major and minor arcs https://cdn.kastatic.org/ka-youtube-converted/U2W7HPyC0cM.mp4/U2W7HPyC0cM.mp4 672 Circle basics https://www.khanacademy.org/math/geometry/hs-geo-circles/hs-geo-circle-basics/v/informal-argument-for-the-area-of-circle-formula 2022-10-07T00:00:24.225559754Z Area of a circle intuition Using triangles to create an informal argument for the area of a circle formula. video https://cdn.kastatic.org/ka_thumbnails_cache/9da1aa53-79ce-4424-af96-fcec5232ec16_1280_720_base.png Area of a circle intuition Using triangles to create an informal argument for the area of a circle formula. https://cdn.kastatic.org/ka-youtube-converted/a2L27dTOyHk.mp4/a2L27dTOyHk.mp4 566 Circle basics https://www.khanacademy.org/math/geometry/hs-geo-circles/hs-geo-circle-basics/v/seeing-circle-similarity-through-translation-and-dilation 2022-10-07T00:00:24.225559754Z Proof: all circles are similar Watch Sal informally prove that all circles are similar by showing how we can translate then dilate any circle onto another. video https://cdn.kastatic.org/ka_thumbnails_cache/b032674a-6e17-4327-a522-af93235d8c2b_1280_720_base.png Proof: all circles are similar Watch Sal informally prove that all circles are similar by showing how we can translate then dilate any circle onto another. https://cdn.kastatic.org/ka-youtube-converted/tcQjJssEMgo.mp4/tcQjJssEMgo.mp4 95 Circle basics https://www.khanacademy.org/math/geometry/hs-geo-similarity/hs-geo-similarity-definitions/v/testing-similarity-through-transformations 2023-05-12T21:01:01.897246564Z Similar shapes & transformations Two shapes are similar if we can change one shape into the other using rigid transformations (like moving or rotating) and dilations (making it bigger or smaller). Other kinds of transformations can change the angles or the ratios of lengths in a figure. If we need those types of transformations, the shapes are not similar. Sal Khan video https://cdn.kastatic.org/ka_thumbnails_cache/95165e7e-8131-4ac8-a2d0-7ee788f53bf6_1280_720_base.png Similar shapes & transformations Two shapes are similar if we can change one shape into the other using rigid transformations (like moving or rotating) and dilations (making it bigger or smaller). Other kinds of transformations can change the angles or the ratios of lengths in a figure. If we need those types of transformations, the shapes are not similar. https://cdn.kastatic.org/ka-youtube-converted/H-YuW_uckz4.mp4/H-YuW_uckz4.mp4 158 Circle basics https://www.khanacademy.org/math/geometry/hs-geo-similarity/hs-geo-similarity-definitions/e/exploring-angle-preserving-transformations-and-similarity 2026-03-09T04:30:46.094426574Z Similarity & transformations Given a pair of figures in the coordinate plane, determine whether they are similar based on whether it is possible to map one to the other using angle-preserving transformations. Tomer Gal exercise