https://www.khanacademy.org/math/geometry/hs-geo-transformations/hs-geo-intro-euclid/v/euclid-as-the-father-of-geometry 2023-05-12T21:01:01.897246564Z Euclid as the father of geometry Euclid, often called the father of geometry, changed the way we learn about shapes with his 13-book series, Euclid's Elements. He used basic ideas called axioms or postulates to create solid proofs and figure out new ideas called theorems and propositions. Studying Euclidean geometry helps us think better and solve problems more effectively. Sal Khan video https://cdn.kastatic.org/googleusercontent/U3qpZvpB6_cxRE3OqCIUB4rNpeHO60MRUiv90BzXvu_PpbHbKx2dV17kpVDj7_wRvYOBZGKnDwAkB_x-0saGg_o Euclid as the father of geometry Euclid, often called the father of geometry, changed the way we learn about shapes with his 13-book series, Euclid's Elements. He used basic ideas called axioms or postulates to create solid proofs and figure out new ideas called theorems and propositions. Studying Euclidean geometry helps us think better and solve problems more effectively. https://cdn.kastatic.org/ka-youtube-converted/WqzK3UAXaHs.mp4/WqzK3UAXaHs.mp4 503 Fundamental Concepts of Geometry https://www.khanacademy.org/math/class-9-tg/x06d55bfa213a79fd:the-elements-of-geometry/x06d55bfa213a79fd:axioms-and-postulates/e/concepts-of-euclid-s-geometry 2026-01-13T12:52:09.519257972Z Concepts of Euclid's geometry This exercise is made for the new ncert and involves concepts from euclid's geometry Devashish Phadnis exercise https://www.khanacademy.org/math/geometry/hs-geo-transformations/hs-geo-intro-euclid/v/language-and-notation-of-basic-geometry 2023-05-07T10:16:56.874628902Z Terms & labels in geometry Explore geometry fundamentals, including points, line segments, rays, and lines. Understand dimensions and how these elements form shapes and patterns. Learn key geometric terms like colinear points, midpoints, and vertices, and enhance your knowledge of geometry. Improve your skills and discover the world of shapes and space. Sal Khan video https://cdn.kastatic.org/googleusercontent/JZ8W-h9naNsX4Bu7I3J_5qfWIjAykN14mxQkvlXIwmb6-7InlR0-0Dj2pRG-BSUJK9iu7Z1-byiuEnQmU43OG9lNJA Terms & labels in geometry Explore geometry fundamentals, including points, line segments, rays, and lines. Understand dimensions and how these elements form shapes and patterns. Learn key geometric terms like colinear points, midpoints, and vertices, and enhance your knowledge of geometry. Improve your skills and discover the world of shapes and space. https://cdn.kastatic.org/ka-youtube-converted/il0EJrY64qE.mp4/il0EJrY64qE.mp4 778 Fundamental Concepts of Geometry https://www.khanacademy.org/math/cc-fourth-grade-math/plane-figures/imp-lines-line-segments-and-rays/e/recognizing_rays_lines_and_line_segments 2025-09-29T06:00:57.283947377Z Identify points, lines, line segments, rays, and angles Recognize points, lines, line segments, rays, and angles in geometric figures. Christopher Wobbles Seymour exercise https://www.khanacademy.org/math/class-8-od/x97648b3e69d960e3:fundamental-concepts-of-geometry-odia-class-8/x97648b3e69d960e3:undefined-terms-and-related-postulates-odia-class-8/v/euclid-s-postulates-3-4-5 2025-07-23T04:52:03.842434868Z Euclid's Postulates - 3 ,4 ,5 Struggling to visualize Euclid’s postulates and how planes actually work? This video makes it simple by using clear visuals and real-world examples to explain Postulates 3, 4, and 5. You'll learn what a plane really is, how points and lines interact with it, and how these foundational ideas shape geometry. A perfect starting point for building strong geometric intuition! Khan Academy video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Euclid's Postulates - 3 ,4 ,5 Struggling to visualize Euclid’s postulates and how planes actually work? This video makes it simple by using clear visuals and real-world examples to explain Postulates 3, 4, and 5. You'll learn what a plane really is, how points and lines interact with it, and how these foundational ideas shape geometry. A perfect starting point for building strong geometric intuition! https://cdn.kastatic.org/ka-youtube-converted/TTPl8PZID_Y.mp4/TTPl8PZID_Y.mp4 501 Fundamental Concepts of Geometry https://www.khanacademy.org/math/revision-term-1-tg-math-lass-6/x0ef789b44aba665e:week-3/x0ef789b44aba665e:measures-of-lines-and-angles/v/parallel-and-intersecting-lines 2024-05-29T15:05:13.425727304Z Parallel and Intersecting lines Description This video describes the concept of parallel and intersecting lines this video piece is a part of video "Basic geometrical terms" Devashish Phadnis video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Parallel and Intersecting lines Description This video describes the concept of parallel and intersecting lines this video piece is a part of video "Basic geometrical terms" https://cdn.kastatic.org/ka-youtube-converted/ypHqclZK1Os.mp4/ypHqclZK1Os.mp4 123 Fundamental Concepts of Geometry https://www.khanacademy.org/math/class-9-tg/x06d55bfa213a79fd:lines-and-angles/x06d55bfa213a79fd:new-lesson/e/identifying-parallel-and-intersecting-lines 2024-08-26T09:59:32.008181873Z Identifying parallel and intersecting lines This exercise is curated for new ncert for the lessons parallel and intersecting lines and includes problems from some other exercises specially curated for the skills of the lesson from unit : Basic geometrical ideas. Devashish Phadnis exercise https://www.khanacademy.org/math/cc-seventh-grade-math/cc-7th-geometry/cc-7th-angles/v/angle-basics 2021-06-30T20:49:32Z Angles: introduction Two rays that share the same endpoint form an angle. Learn about angles and the parts of an angle, like the vertex. Sal Khan video https://cdn.kastatic.org/googleusercontent/OiWEcQJuUwuBizhFxcflrEDtYQE0F8Hl2xR3vqY3VA0eSSYntfsQiuoz69dkBWU9pqdIe2Sy99yqWwlJjX_E1JFmLQ Angles: introduction Two rays that share the same endpoint form an angle. Learn about angles and the parts of an angle, like the vertex. https://cdn.kastatic.org/ka-youtube-converted/H-de6Tkxej8.mp4/H-de6Tkxej8.mp4 409 Fundamental Concepts of Geometry https://www.khanacademy.org/math/cc-seventh-grade-math/cc-7th-geometry/cc-7th-angles/e/naming-angles 2025-09-26T06:00:44.003534089Z Name angles Name angles by their vertex, endpoints, or labels.   Sandy Knight exercise https://www.khanacademy.org/math/class-6-ncf/x04ca845a9a148c80:lines-and-angles/x04ca845a9a148c80:angles/e/identifying-parts-of-an-angle-6th 2026-04-07T22:59:30.107127435Z Identify parts of an angle Identifying parts of an angle supriya exercise https://www.khanacademy.org/math/cc-fourth-grade-math/imp-geometry-2/imp-measuring-angles/v/measuring-angles-in-degrees 2021-06-30T20:49:32Z Measuring angles in degrees Learn how to measure an angle with a protractor.   Sal Khan video https://cdn.kastatic.org/googleusercontent/AUN8zIwamVCnRbVrbNkTeBO9SpKe7AxHlEaNRb5uRVice-wM0qmnW-YuL_KiAeC99oc3B1LtSsEEtRXjOhR3PGg5 Measuring angles in degrees Learn how to measure an angle with a protractor.   https://cdn.kastatic.org/ka-youtube-converted/92aLiyeQj0w.mp4/92aLiyeQj0w.mp4 502 Fundamental Concepts of Geometry https://www.khanacademy.org/math/cc-fourth-grade-math/imp-geometry-2/imp-measuring-angles/e/drawing-angles 2026-04-07T23:36:17.218592739Z Draw angles Use a protractor to construct angles. Sandy Knight exercise https://www.khanacademy.org/math/geometry/hs-geo-congruence/hs-geo-bisectors/v/constructing-an-angle-bisector-using-a-compass-and-straightedge 2021-02-16T16:08:13Z Geometric constructions: angle bisector Sal constructs a line that bisects a given angle using compass and straightedge. Sal Khan video https://cdn.kastatic.org/googleusercontent/k0ShVOtWKk8bpYbdkwztYCR_s299KJ7K2IC6cbiEn3WNlW88vonoAm9h67WtxvGHEFGXes-Y5in6opSJHr702xMy Geometric constructions: angle bisector Sal constructs a line that bisects a given angle using compass and straightedge. https://cdn.kastatic.org/ka-youtube-converted/KNr52iFk7n4.mp4/KNr52iFk7n4.mp4 137 Fundamental Concepts of Geometry https://www.khanacademy.org/math/class-6-ncf/x04ca845a9a148c80:lines-and-angles/x04ca845a9a148c80:types-of-angles-and-their-measures/v/acute-obtuse-and-reflex-angles 2024-05-22T06:22:00.374380016Z Acute, Obtuse and Reflex angles Learn about Acute , obtuse and reflex angles introduction Devashish Phadnis video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Acute, Obtuse and Reflex angles Learn about Acute , obtuse and reflex angles introduction https://cdn.kastatic.org/ka-youtube-converted/Jj8XhAb1-zA.mp4/Jj8XhAb1-zA.mp4 208 Fundamental Concepts of Geometry https://www.khanacademy.org/math/geometry-home/geometry-angles/angle-types/e/drawing-right--acute--and-obtuse-angles 2025-02-13T04:57:25.728250847Z Draw right, acute, and obtuse angles Create an acute, right, or obtuse angle using a given vertex. Justin Helps exercise https://www.khanacademy.org/math/cc-seventh-grade-math/cc-7th-geometry/cc-7th-angles/v/complementary-and-supplementary-angles 2021-07-02T09:35:33Z Complementary & supplementary angles Learn about complementary and supplementary angles, as well as the definitions of adjacent and straight angles. Sal Khan video https://cdn.kastatic.org/googleusercontent/qDVRlJF769umQwhK0k5Gws2kWYPwSZplfCVSDfogMTaAgwYWW_U-6rLm70oo6ChLWcrKMyh4Np5FI6xpBfkMBSDydw Complementary & supplementary angles Learn about complementary and supplementary angles, as well as the definitions of adjacent and straight angles. https://cdn.kastatic.org/ka-youtube-converted/BTnAlNSgNsY.mp4/BTnAlNSgNsY.mp4 511 Fundamental Concepts of Geometry https://www.khanacademy.org/math/cc-seventh-grade-math/cc-7th-geometry/cc-7th-angles/e/complementary_and_supplementary_angles 2025-02-06T19:34:52.815179935Z Complementary and supplementary angles (visual) Use your knowledge about complementary and supplementary angles to find missing angles. Marcia Lee exercise https://www.khanacademy.org/math/cc-seventh-grade-math/cc-7th-geometry/cc-7th-angles/e/complementary-and-supplementary-angles--no-visual- 2024-09-05T20:39:26.312313729Z Complementary and supplementary angles (no visual) Use complementary and supplementary angles to solve for a missing angle measure. Lindsay exercise https://www.khanacademy.org/math/cc-seventh-grade-math/cc-7th-geometry/cc-7th-angles/v/angles-at-the-intersection-of-two-lines 2021-07-02T09:35:28Z Vertical angles By using our knowledge of supplementary, adjacent, and vertical angles, we can solve problems involving the intersection of two lines. Including this one! Sal Khan video https://cdn.kastatic.org/googleusercontent/vG8VY_P_fY1oMY1y1aqral5PJT2HpHQeBDB_qPJO6AdEutPu7HNvYS_ydXRTqTtJ3fzmb5rt85ux8oOh9hDwGn2_QQ Vertical angles By using our knowledge of supplementary, adjacent, and vertical angles, we can solve problems involving the intersection of two lines. Including this one! https://cdn.kastatic.org/ka-youtube-converted/_7aUxFzTG5w.mp4/_7aUxFzTG5w.mp4 439 Fundamental Concepts of Geometry https://www.khanacademy.org/math/cc-seventh-grade-math/cc-7th-geometry/cc-7th-angles/e/identifying-supplementary-complementary-vertical 2026-03-09T04:30:46.094426574Z Identifying supplementary, complementary, and vertical angles Practice telling whether two angles are supplementary, complementary, or vertical. Ben exercise