https://www.khanacademy.org/math/cc-eighth-grade-math/cc-8th-geometry/cc-8th-angles-between-lines/v/angles-formed-by-parallel-lines-and-transversals 2023-05-12T21:01:01.897246564Z Angles, parallel lines, & transversals Parallel lines are lines in the same plane that go in the same direction and never intersect. When a third line, called a transversal, crosses these parallel lines, it creates angles. Some angles are equal, like vertical angles (opposite angles) and corresponding angles (same position at each intersection). Sal Khan video https://cdn.kastatic.org/googleusercontent/Vz_NMEoL9pcokuLJEAFY_U-n9SIzbtc56vA_P8hGFXLXAZEIdmfteizOxfIHqBk4kThnx6aglnEoGdRMahNp4OyW3w Angles, parallel lines, & transversals Parallel lines are lines in the same plane that go in the same direction and never intersect. When a third line, called a transversal, crosses these parallel lines, it creates angles. Some angles are equal, like vertical angles (opposite angles) and corresponding angles (same position at each intersection). https://cdn.kastatic.org/ka-youtube-converted/H-E5rlpCVu4.mp4/H-E5rlpCVu4.mp4 427 Angles of parallel lines and transversal https://www.khanacademy.org/math/cc-eighth-grade-math/cc-8th-geometry/cc-8th-angles-between-lines/e/parallel_lines_1 2026-03-24T23:41:07.080866137Z Angle relationships with parallel lines Find missing angles given two parallel lines and a transversal. Marcia Lee exercise https://www.khanacademy.org/math/cc-eighth-grade-math/cc-8th-geometry/cc-8th-angles-between-lines/v/figuring-out-angles-between-transversal-and-parallel-lines 2023-05-12T21:01:01.897246564Z Missing angles with a transversal When a third line called a transversal crosses two parallel lines, we can find the measures of angles using properties like corresponding angles, vertical angles, and supplementary angles. If we know just one of the angle measurements, these properties help us find all the missing angle measurements. Sal Khan video https://cdn.kastatic.org/googleusercontent/Jc7Hc_hUwIAHvvJpv_xjYjVmNGH5TEE0q90O7tSCCMK6BQ1fOzUe2zl-KCs-2bpIZZ-87m_tAVueoL37Wiy8QB5SOw Missing angles with a transversal When a third line called a transversal crosses two parallel lines, we can find the measures of angles using properties like corresponding angles, vertical angles, and supplementary angles. If we know just one of the angle measurements, these properties help us find all the missing angle measurements. https://cdn.kastatic.org/ka-youtube-converted/2WjGD3LZEWo.mp4/2WjGD3LZEWo.mp4 136 Angles of parallel lines and transversal https://www.khanacademy.org/math/cc-eighth-grade-math/cc-8th-geometry/cc-8th-angles-between-lines/v/using-algebra-to-find-measures-of-angles-formed-from-transversal 2025-06-10T12:18:12.264638758Z Measures of angles formed by a transversal When parallel lines are crossed by another line called a transversal, special angles are formed. We can find the measures of these angles using algebra and the relationships between the angles, like congruent angles and supplementary angles. Once we solve for the variable, we use that value to figure out the angle measures. Sal Khan video https://cdn.kastatic.org/googleusercontent/jH5ENXnD6D-PN3MBbpChj1DItsL6-IBBlBy4CSWjNhZisvLGEEEuEoyVVhW6tRAfsndWS8O7Q7v4u9lIu_ugTO9D Measures of angles formed by a transversal When parallel lines are crossed by another line called a transversal, special angles are formed. We can find the measures of these angles using algebra and the relationships between the angles, like congruent angles and supplementary angles. Once we solve for the variable, we use that value to figure out the angle measures. https://cdn.kastatic.org/ka-youtube-converted/Ld7Vxb5XV6A.mp4/Ld7Vxb5XV6A.mp4 281 Angles of parallel lines and transversal https://www.khanacademy.org/math/cc-eighth-grade-math/cc-8th-geometry/cc-8th-angles-between-lines/e/parallel_lines_2 2026-03-31T21:47:15.031073863Z Equation practice with angles Solve for angle measures on angles formed by parallel lines and a transversal, where the angle measures are given as linear expressions. Matt Wahl exercise https://www.khanacademy.org/math/revision-term-1-mh-math-class-7/x0bdc8a5f9d8ec377:week-2/x0bdc8a5f9d8ec377:angles-and-pairs-of-angles/v/triangle-exterior-angle-example-indian-accent 2025-06-04T10:04:13.13703146Z Triangle exterior angle example An exterior angle is formed outside a triangle by extending a side. Its measure is equal to the sum of the two non-adjacent interior angle measures, thanks to the fact that all angle measures in a triangle add up to 180 degrees. Skyloom (Dubbing) video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Triangle exterior angle example An exterior angle is formed outside a triangle by extending a side. Its measure is equal to the sum of the two non-adjacent interior angle measures, thanks to the fact that all angle measures in a triangle add up to 180 degrees. https://cdn.kastatic.org/ka-youtube-converted/g2bHflif-VI.mp4/g2bHflif-VI.mp4 349 Angles of parallel lines and transversal https://www.khanacademy.org/math/cc-eighth-grade-math/cc-8th-geometry/cc-8th-triangle-angles/v/challenging-triangle-angle-problem 2023-06-02T19:09:07.369858129Z Triangle angle challenge problem Learn about the sum of exterior angles in a polygon, specifically a pentagon. We find out that the sum of exterior angles is always the same, no matter the shape of the pentagon. To understand this, we use interior angles and divide the pentagon into triangles. Sal Khan video https://cdn.kastatic.org/googleusercontent/OKCwbZirqxkYi7J87sawZBCWwUgjTOIU0Ml06C_nddO7-hf9QBCZNPBU6hbs2T85baV2XbNeGzw7SrIIgJ42Q-k Triangle angle challenge problem Learn about the sum of exterior angles in a polygon, specifically a pentagon. We find out that the sum of exterior angles is always the same, no matter the shape of the pentagon. To understand this, we use interior angles and divide the pentagon into triangles. https://cdn.kastatic.org/ka-youtube-converted/95logvV8nXY.mp4/95logvV8nXY.mp4 517 Angles of parallel lines and transversal https://www.khanacademy.org/math/cc-eighth-grade-math/cc-8th-geometry/cc-8th-triangle-angles/v/finding-more-angles 2023-06-02T19:09:07.369858129Z Triangle angle challenge problem 2 Find angle measures in triangles when the given measures are algebraic expressions. The key idea is that the sum of all angles in a triangle is always 180 degrees. We can also use parallel lines and transversals to find angle measures. Sal Khan video https://cdn.kastatic.org/googleusercontent/SVQhkWdZHtQhIhzAJ5GAIj4P77hsA3Zy0xclN-77OmMo60KSWLLH-P4AL5bO2bYznZPehE1BSRBXDuQ28E-_qfFxCg Triangle angle challenge problem 2 Find angle measures in triangles when the given measures are algebraic expressions. The key idea is that the sum of all angles in a triangle is always 180 degrees. We can also use parallel lines and transversals to find angle measures. https://cdn.kastatic.org/ka-youtube-converted/0gzSreH8nUI.mp4/0gzSreH8nUI.mp4 365 Angles of parallel lines and transversal