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bisector-and-perpendicular-line-lesson-19.pptx

  1. 1. ๐‘ซ๐’†๐’‡๐’Š๐’๐’Š๐’•๐’Š๐’๐’ ๐’๐’‡ ๐‘ซ๐’Š๐’”๐’•๐’‚๐’๐’„๐’† ๐’‡๐’“๐’๐’Ž ๐’‚ ๐‘ท๐’๐’Š๐’๐’• ๐’•๐’ ๐’‚ ๐‘ณ๐’Š๐’๐’† The distance from a point to a line is the length of the perpendicular segment from the point to the line. If the point lies on the line, the distance is zero. P C A B The distance from point P to AB is PC. Here PC โŠฅ AB
  2. 2. Theorem 35 A point on the bisector of an angle is equidistant from the sides of the angle. A D G F E C B Given: ๐‘ฉ๐‘ซ bisects โˆ ๐‘จ๐‘ฉ๐‘ช, G lies on ๐‘ฉ๐‘ซ Prove: ๐‘ฎ๐‘ฌ = ๐‘ฎ๐‘ญ
  3. 3. A D G F E C B Given: ๐‘ฉ๐‘ซ bisects โˆ ๐‘จ๐‘ฉ๐‘ช, G lies on ๐‘ฉ๐‘ซ Prove: ๐‘ฎ๐‘ฌ = ๐‘ฎ๐‘ญ ๐’๐ญ๐š๐ญ๐ž๐ฆ๐ž๐ง๐ญ๐ฌ ๐‘๐ž๐š๐ฌ๐จ๐ง๐ฌ 1. ๐๐ƒ bisects โˆ ๐€๐๐‚, G lies on ๐๐ƒ ๐†๐ข๐ฏ๐ž๐ง 2. โˆ ๐€๐๐ƒ โ‰… โˆ ๐‚๐๐ƒ ๐ƒ๐ž๐Ÿ๐ข๐ง๐ข๐ญ๐ข๐จ๐ง ๐จ๐Ÿ ๐€๐ง๐ ๐ฅ๐ž ๐๐ข๐ฌ๐ž๐œ๐ญ๐จ๐ซ 3. ๐†๐„ โŠฅ ๐๐€ ๐†๐… โŠฅ ๐๐‚ ๐ƒ๐ž๐Ÿ๐ข๐ง๐ข๐ญ๐ข๐จ๐ง ๐จ๐Ÿ ๐ญ๐ก๐ž ๐ƒ๐ข๐ฌ๐ญ๐š๐ง๐œ๐ž ๐Ÿ๐ซ๐จ๐ฆ ๐š ๐๐จ๐ข๐ง๐ญ ๐ญ๐จ ๐š ๐‹๐ข๐ง๐ž 4. โˆ ๐†๐„๐ ๐š๐ง๐ โˆ ๐†๐…๐ ๐š๐ซ๐ž ๐ซ๐ข๐ ๐ก๐ญ ๐š๐ง๐ ๐ฅ๐ž๐ฌ. ๐ƒ๐ž๐Ÿ๐ข๐ง๐ข๐ญ๐ข๐จ๐ง ๐จ๐Ÿ ๐๐ž๐ซ๐ฉ๐ž๐ง๐๐ข๐œ๐ฎ๐ฅ๐š๐ซ 5. ๐๐† โ‰… ๐๐† ๐‘๐ž๐Ÿ๐ฅ๐ž๐ฑ๐ข๐ฏ๐ž ๐๐ซ๐จ๐ฉ๐ž๐ซ๐ญ๐ฒ ๐จ๐Ÿ ๐‚๐จ๐ง๐ ๐ซ๐ฎ๐ž๐ง๐œ๐ž 6. โˆ†๐†๐„๐ ๐š๐ง๐ โˆ†๐†๐…๐ ๐š๐ซ๐ž ๐ซ๐ข๐ ๐ก๐ญ ๐ญ๐ซ๐ข๐š๐ง๐ ๐ฅ๐ž๐ฌ. ๐ƒ๐ž๐Ÿ๐ข๐ง๐ข๐ญ๐ข๐จ๐ง ๐จ๐Ÿ ๐‘๐ข๐ ๐ก๐ญ ๐“๐ซ๐ข๐š๐ง๐ ๐ฅ๐ž๐ฌ 7. โˆ†๐†๐„๐ โ‰… โˆ†๐†๐…๐ ๐‡๐ฒ๐ฉ๐จ๐ญ๐ž๐ง๐ฎ๐ฌ๐ž โˆ’ ๐€๐œ๐ฎ๐ญ๐ž ๐€๐ง๐ ๐ฅ๐ž 8. ๐†๐„ โ‰… ๐†๐… ๐‚๐๐‚๐“๐‚ 9. ๐†๐„ = ๐†๐… ๐ƒ๐ž๐Ÿ๐ข๐ง๐ข๐ญ๐ข๐จ๐ง ๐จ๐Ÿ ๐‚๐จ๐ง๐ ๐ซ๐ฎ๐ž๐ง๐ญ ๐’๐ž๐ ๐ฆ๐ž๐ง๐ญ๐ฌ proof:
  4. 4. Theorem 36 A point equidistant from the sides of an angle lies on the bisector of an angle A D G F E C B Given: ๐บ๐ธ โŠฅ ๐ต๐ด; ๐บ๐น โŠฅ ๐ต๐ถ, ๐บ๐ธ = ๐บ๐น Prove: ๐บ lies on the bisector of โˆ ๐ด๐ต๐ถ. ๐‘ท๐’†๐’“๐’‘๐’†๐’๐’…๐’Š๐’„๐’–๐’๐’‚๐’“ ๐‘ฉ๐’Š๐’”๐’†๐’„๐’•๐’๐’“๐’” ๐’๐’‡ ๐’‚ ๐‘บ๐’†๐’ˆ๐’Ž๐’†๐’๐’• Recall that the perpendicular bisector of a segment is a line, ray, segment, or plane that is perpendicular to the segment at its midpoint.
  5. 5. ๐‘ป๐’‰๐’†๐’๐’“๐’†๐’Ž ๐Ÿ‘๐Ÿ• A point on the perpendicular bisector of a segment is equidistant from the endpoint of a segment. C P D B A Given: ๐‘ช๐‘ซ โŠฅ ๐’ƒ๐’Š๐’”๐’†๐’„๐’•๐’๐’“ ๐’๐’‡ ๐‘จ๐‘ฉ, ๐‘ท lies on ๐‘ช๐‘ซ. Prove: ๐‘ท๐‘จ = ๐‘ท๐‘ฉ
  6. 6. C P D B A Given: ๐‘ช๐‘ซ โŠฅ ๐’ƒ๐’Š๐’”๐’†๐’„๐’•๐’๐’“ ๐’๐’‡ ๐‘จ๐‘ฉ, ๐‘ท lies on ๐‘ช๐‘ซ. Prove: ๐‘ท๐‘จ = ๐‘ท๐‘ฉ ๐’‘๐’“๐’๐’๐’‡: ๐‘†๐‘ก๐‘Ž๐‘ก๐‘’๐‘š๐‘’๐‘›๐‘ก๐‘  ๐‘…๐‘’๐‘Ž๐‘ ๐‘œ๐‘›๐‘  1. ๐ถ๐ท โŠฅ bisector of ๐ด๐ต, ๐‘ƒ lies on ๐ถ๐ท. ๐บ๐‘–๐‘ฃ๐‘’๐‘› 2. ๐ท๐‘Ÿ๐‘Ž๐‘ค ๐ด๐‘ƒ ๐‘Ž๐‘›๐‘‘ ๐ต๐‘ƒ. ๐ฟ๐‘–๐‘›๐‘’ ๐‘ƒ๐‘œ๐‘ ๐‘ก๐‘ข๐‘™๐‘Ž๐‘ก๐‘’ 3. ๐ถ๐ท โŠฅ ๐ด๐ต; ๐ท ๐‘–๐‘  ๐‘กโ„Ž๐‘’ ๐‘š๐‘–๐‘‘๐‘๐‘œ๐‘–๐‘›๐‘ก ๐‘œ๐‘“ ๐ด๐ต. ๐ท๐‘’๐‘“๐‘–๐‘›๐‘–๐‘ก๐‘–๐‘œ๐‘› ๐‘œ๐‘“ ๐‘ƒ๐‘’๐‘Ÿ๐‘๐‘’๐‘›๐‘‘๐‘–๐‘๐‘ข๐‘™๐‘Ž๐‘Ÿ ๐ต๐‘–๐‘ ๐‘’๐‘๐‘ก๐‘œ๐‘Ÿ 4. โˆ ๐‘ƒ๐ท๐ด ๐‘Ž๐‘›๐‘‘ โˆ ๐‘ƒ๐ท๐ต ๐‘Ž๐‘Ÿ๐‘’ ๐‘Ÿ๐‘–๐‘”โ„Ž๐‘ก ๐‘Ž๐‘›๐‘”๐‘™๐‘’. ๐ท๐‘’๐‘“๐‘–๐‘›๐‘–๐‘ก๐‘–๐‘œ๐‘› ๐‘œ๐‘“ ๐‘ƒ๐‘’๐‘Ÿ๐‘๐‘’๐‘›๐‘‘๐‘–๐‘๐‘ข๐‘™๐‘Ž๐‘Ÿ 5. โˆ†๐‘ƒ๐ท๐ด ๐‘Ž๐‘›๐‘‘ โˆ†๐‘ƒ๐ท๐ต ๐‘Ž๐‘Ÿ๐‘’ ๐‘Ÿ๐‘–๐‘”โ„Ž๐‘ก ๐‘Ž๐‘›๐‘”๐‘™๐‘’. ๐ท๐‘’๐‘“๐‘–๐‘›๐‘–๐‘ก๐‘–๐‘œ๐‘› ๐‘œ๐‘“ ๐‘…๐‘–๐‘”โ„Ž๐‘ก ๐‘‡๐‘Ÿ๐‘–๐‘Ž๐‘›๐‘”๐‘™๐‘’๐‘  6. ๐ด๐ท โ‰… ๐ต๐ท ๐ท๐‘’๐‘“๐‘–๐‘›๐‘–๐‘ก๐‘–๐‘œ๐‘› ๐‘œ๐‘“ ๐‘Ž ๐‘€๐‘–๐‘‘๐‘๐‘œ๐‘–๐‘›๐‘ก 7. ๐‘ƒ๐ท โ‰… ๐‘ƒ๐ท ๐‘…๐‘’๐‘“๐‘™๐‘’๐‘ฅ๐‘–๐‘ฃ๐‘’ ๐‘ƒ๐‘Ÿ๐‘œ๐‘๐‘’๐‘Ÿ๐‘ก๐‘ฆ ๐‘œ๐‘“ ๐ถ๐‘œ๐‘›๐‘”๐‘Ÿ๐‘ข๐‘’๐‘›๐‘๐‘’ 8. โˆ†๐‘ƒ๐ท๐ด โ‰… โˆ†๐‘ƒ๐ท๐ต ๐ฟ๐‘’๐‘” โˆ’ ๐ฟ๐‘’๐‘” ๐‘‡โ„Ž๐‘’๐‘œ๐‘Ÿ๐‘’๐‘š 9. ๐‘ƒ๐ด โ‰… ๐‘ƒ๐ต ๐ถ๐‘ƒ๐ถ๐‘‡๐ถ 10. ๐‘ƒ๐ด = ๐‘ƒ๐ต ๐ท๐‘’๐‘“๐‘–๐‘›๐‘–๐‘ก๐‘–๐‘œ๐‘› ๐‘œ๐‘“ ๐ถ๐‘œ๐‘›๐‘”๐‘Ÿ๐‘ข๐‘’๐‘›๐‘ก ๐‘†๐‘’๐‘”๐‘š๐‘’๐‘›๐‘ก๐‘ 
  7. 7. ๐‘ป๐’‰๐’†๐’๐’“๐’†๐’Ž ๐Ÿ‘๐Ÿ– A point equidistant from the endpoint of a segment lies on the perpendicular bisector of a segment. C P D B A Given: ๐๐€ = ๐๐ Prove: P lies on the perpendicular bisector of AB.
  8. 8. C P D B A Given: ๐๐€ = ๐๐ Prove: P lies on the perpendicular bisector of AB. ๐’‘๐’“๐’๐’๐’‡: ๐‘บ๐’•๐’‚๐’•๐’†๐’Ž๐’†๐’๐’•๐’” ๐‘น๐’†๐’‚๐’”๐’๐’๐’” 1. ๐‘ณ๐’†๐’• ๐‘ซ ๐’ƒ๐’† ๐’•๐’‰๐’† ๐’Ž๐’Š๐’…๐’‘๐’๐’Š๐’๐’• ๐’๐’‡ ๐‘จ๐‘ฉ ๐‘ป๐’‰๐’†๐’๐’“๐’†๐’Ž ๐Ÿ”. ๐‘ฌ๐’—๐’†๐’“๐’š ๐’”๐’†๐’ˆ๐’Ž๐’†๐’๐’• ๐’‰๐’‚๐’” ๐’†๐’™๐’‚๐’„๐’•๐’๐’š ๐’๐’๐’† ๐’Ž๐’Š๐’…๐’‘๐’๐’Š๐’๐’• 2. ๐‘จ๐‘ซ โ‰… ๐‘ฉ๐‘ซ ๐‘ซ๐’†๐’‡๐’Š๐’๐’Š๐’•๐’Š๐’๐’ ๐’๐’‡ ๐’‚ ๐‘ด๐’Š๐’…๐’‘๐’๐’Š๐’๐’• 3. ๐‘ซ๐’“๐’‚๐’˜ ๐’๐’Š๐’๐’† ๐‘ท๐‘ซ ๐‘ณ๐’Š๐’๐’† ๐‘ท๐’๐’”๐’•๐’–๐’๐’‚๐’•๐’† 4. ๐‘ท๐‘ซ โ‰… ๐‘ท๐‘ซ ๐‘น๐’†๐’‡๐’๐’†๐’™๐’Š๐’—๐’† ๐‘ท๐’“๐’๐’‘๐’†๐’“๐’•๐’š ๐’๐’‡ ๐‘ช๐’๐’๐’ˆ๐’“๐’–๐’†๐’๐’„๐’† 5. ๐‘ท๐‘จ = ๐‘ท๐‘ฉ ๐‘ฎ๐’Š๐’—๐’†๐’ 6. โˆ†๐‘ท๐‘ซ๐‘จ โ‰… โˆ†๐‘ท๐‘ซ๐‘ฉ ๐‘บ๐‘บ๐‘บ ๐‘ท๐’๐’”๐’•๐’–๐’๐’‚๐’•๐’† 7. โˆ ๐‘ท๐‘ซ๐‘จ โ‰… โˆ ๐‘ท๐‘ซ๐‘ฉ ๐‘ช๐‘ท๐‘ช๐‘ป๐‘ช 8. โˆ ๐‘ท๐‘ซ๐‘จ ๐’‚๐’๐’… โˆ ๐‘ท๐‘ซ๐‘ฉ ๐’‡๐’๐’“๐’Ž ๐’‚ ๐’๐’Š๐’๐’†๐’‚๐’“ ๐’‘๐’‚๐’Š๐’“. ๐‘ซ๐’†๐’‡๐’Š๐’๐’Š๐’•๐’Š๐’๐’ ๐’๐’‡ ๐‘ณ๐’Š๐’๐’†๐’‚๐’“ ๐‘ท๐’‚๐’Š๐’“ 9.โˆ ๐‘ท๐‘ซ๐‘จ ๐’‚๐’๐’… โˆ ๐‘ท๐‘ซ๐‘ฉ ๐’‚๐’“๐’† ๐’”๐’–๐’‘๐’‘๐’๐’†๐’Ž๐’†๐’๐’•๐’‚๐’“๐’š. ๐‘ณ๐’Š๐’๐’†๐’‚๐’“ ๐‘ท๐’‚๐’Š๐’“ ๐‘ท๐’๐’”๐’•๐’–๐’๐’‚๐’•๐’† 10. โˆ ๐‘ท๐‘ซ๐‘จ ๐’‚๐’๐’… โˆ ๐‘ท๐‘ซ๐‘ฉ ๐’‚๐’“๐’† ๐’“๐’Š๐’ˆ๐’‰๐’• ๐’‚๐’๐’ˆ๐’๐’† ๐‘ป๐’‰๐’†๐’๐’“๐’†๐’Ž ๐Ÿ๐Ÿ”. ๐‘ฐ๐’‡ ๐’•๐’˜๐’ ๐’‚๐’๐’ˆ๐’๐’†๐’” ๐’‚๐’“๐’† ๐’ƒ๐’๐’•๐’‰ ๐’„๐’๐’๐’ˆ๐’“๐’–๐’†๐’๐’• ๐’‚๐’๐’… ๐’”๐’–๐’‘๐’‘๐’๐’†๐’Ž๐’†๐’๐’•๐’‚๐’“๐’š, ๐’•๐’‰๐’†๐’ ๐’†๐’‚๐’„๐’‰ ๐’Š๐’” ๐’‚ ๐’“๐’Š๐’ˆ๐’‰๐’• ๐’‚๐’๐’ˆ๐’๐’†.
  9. 9. ๐‘ป๐’‰๐’†๐’๐’“๐’†๐’Ž ๐Ÿ‘๐Ÿ— If a line contains two points each of which is equidistant from the endpoints of the segment, then the line is the perpendicular bisector of the segment. C P D B A Given: AP=BP, AC=BC Prove: PD is the โŠฅ bisector of AB.
  10. 10. C P D B A Given: AP=BP, AC=BC Prove: PD is the โŠฅ bisector of AB. ๐’๐ญ๐š๐ญ๐ž๐ฆ๐ž๐ง๐ญ๐ฌ ๐‘๐ž๐š๐ฌ๐จ๐ง๐ฌ 1. ๐€๐ โ‰… ๐๐, ๐€๐‚ โ‰… ๐๐‚ ๐†๐ข๐ฏ๐ž๐ง ๐š๐ง๐ ๐ƒ๐ž๐Ÿ๐ข๐ง๐ข๐ญ๐ข๐จ๐ง ๐จ๐Ÿ ๐‚๐จ๐ง๐ ๐ซ๐ฎ๐ž๐ง๐ญ ๐’๐ž๐ ๐ฆ๐ž๐ง๐ญ๐ฌ 2. ๐๐‚ โ‰… ๐๐‚ ๐‘๐ž๐Ÿ๐ฅ๐ž๐ฑ๐ข๐ฏ๐ž ๐๐ซ๐จ๐ฉ๐ž๐ซ๐ญ๐ฒ ๐จ๐Ÿ ๐‚๐จ๐ง๐ ๐ซ๐ฎ๐ž๐ง๐œ๐ž 3. โˆ†๐๐‚๐€ โ‰… โˆ†๐๐‚๐ ๐’๐’๐’ ๐๐จ๐ฌ๐ญ๐ฎ๐ฅ๐š๐ญ๐ž 4. โˆ ๐€๐๐ƒ โ‰… โˆ ๐๐๐ƒ ๐‚๐๐‚๐“๐‚ 5. ๐๐ƒ โ‰… ๐๐ƒ ๐‘๐ž๐Ÿ๐ฅ๐ž๐ฑ๐ข๐ฏ๐ž ๐๐ซ๐จ๐ฉ๐ž๐ซ๐ญ๐ฒ ๐จ๐Ÿ ๐‚๐จ๐ง๐ ๐ซ๐ฎ๐ž๐ง๐œ๐ž 6. โˆ†๐€๐๐ƒ โ‰… โˆ†๐๐๐ƒ ๐’๐€๐’ ๐๐จ๐ฌ๐ญ๐ฎ๐ฅ๐š๐ญ๐ž 7. ๐€๐ƒ โ‰… ๐๐ƒ ๐‚๐๐‚๐“๐‚ 8. ๐ƒ ๐ข๐ฌ ๐ญ๐ก๐ž ๐ฆ๐ข๐๐ฉ๐จ๐ข๐ง๐ญ ๐จ๐Ÿ ๐€๐ ๐ƒ๐ž๐Ÿ๐ข๐ง๐ข๐ญ๐ข๐จ๐ง ๐จ๐Ÿ ๐Œ๐ข๐๐ฉ๐จ๐ข๐ง๐ญ 9. โˆ ๐๐ƒ๐€ โ‰… โˆ ๐๐ƒ๐ ๐‚๐๐‚๐“๐‚ 10.โˆ ๐๐ƒ๐€ ๐š๐ง๐ โˆ ๐๐ƒ๐ ๐Ÿ๐จ๐ซ๐ฆ ๐š ๐ฅ๐ข๐ง๐ž๐š๐ซ ๐Ÿ๐ข๐ซ๐ฆ ๐ƒ๐ž๐Ÿ๐ข๐ง๐ข๐ญ๐ข๐จ๐ง ๐จ๐Ÿ ๐‹๐ข๐ง๐ž๐š๐ซ ๐๐š๐ข๐ซ 11. โˆ ๐๐ƒ๐€ ๐š๐ง๐ โˆ ๐๐ƒ๐ ๐š๐ซ๐ž ๐ฌ๐ฎ๐ฉ๐ฉ๐ฅ๐ž๐ฆ๐ž๐ง๐ญ๐š๐ซ๐ฒ ๐‹๐ข๐ง๐ž๐š๐ซ ๐๐š๐ข๐ซ ๐๐จ๐ฌ๐ญ๐ฎ๐ฅ๐š๐ญ๐ž 12. โˆ ๐๐ƒ๐€ ๐š๐ง๐ โˆ ๐๐ƒ๐ ๐š๐ซ๐ž ๐ซ๐ข๐ ๐ก๐ญ ๐š๐ง๐ ๐ฅ๐ž๐ฌ ๐“๐ก๐ž๐จ๐ซ๐ž๐ฆ ๐Ÿ๐Ÿ”. ๐ˆ๐Ÿ ๐ญ๐ฐ๐จ ๐š๐ง๐ ๐ฅ๐ž๐ฌ ๐š๐ซ๐ž ๐›๐จ๐ญ๐ก ๐œ๐จ๐ง๐ ๐ซ๐ฎ๐ž๐ง๐ญ ๐š๐ง๐ ๐ฌ๐ฎ๐ฉ๐ฉ๐ฅ๐ž๐ฆ๐ž๐ง๐ญ๐š๐ซ๐ฒ, ๐ญ๐ก๐ž๐ง ๐ž๐š๐œ๐ก ๐ข๐ฌ ๐š ๐ซ๐ข๐ ๐ก๐ญ ๐š๐ง๐ ๐ฅ๐ž 13. ๐๐ƒ ๐ข๐ฌ ๐ญ๐ก๐ž โŠฅ ๐›๐ข๐ฌ๐ž๐œ๐ญ๐จ๐ซ ๐จ๐Ÿ ๐€๐ ๐ƒ๐ž๐Ÿ๐ข๐ง๐ข๐ญ๐ข๐จ๐ง ๐จ๐Ÿ ๐ฉ๐ž๐ซ๐ฉ๐ž๐ง๐๐ข๐œ๐ฎ๐ฅ๐š๐ซ ๐๐ข๐ฌ๐ž๐œ๐ญ๐จ๐ซ proof:
  11. 11. ๐‘ป๐’‰๐’†๐’๐’“๐’†๐’Ž ๐Ÿ’๐ŸŽ In a plane, through a given points on a line, there is exactly one line perpendicular to the line. R S M P Q Given: MQ and point P on MQ Prove: a. There is at least on line PR โŠฅ MQ b. There is only one line PR โŠฅ MQ Part 1: Show that there is one line ๐‘ท๐‘น โŠฅ ๐‘ด๐‘ธ through point P. Through the end point of ๐‘ท๐‘ธ , ray ๐‘ท๐‘น can be constructed in such a way that ๐’Žโˆ ๐‘น๐‘ท๐‘ธ = ๐Ÿ—๐ŸŽ. โˆ ๐‘น๐‘ท๐‘ธis therefore a right angle and hence, by the definition of perpendicular, ๐‘ท๐‘น โŠฅ ๐‘ด๐‘ธ . Since rays ๐‘ท๐‘น โŠฅ ๐‘ท๐‘ธ are contained in ๐‘ท๐‘น ๐’‚๐’๐’… ๐‘ด๐‘ธ , respectively, therefore ๐‘ท๐‘น โŠฅ ๐‘ด๐‘ธ .
  12. 12. Part 2: Show that ๐‘ท๐‘น ๐’Š๐’” ๐’•๐’‰๐’† ๐’๐’๐’๐’š ๐’๐’Š๐’๐’† โŠฅ ๐‘ด๐‘ธ through P. There is only one line ๐‘ท๐‘น โŠฅ ๐‘ด๐‘ธ or other than ๐‘ท๐‘น there is another line ๐‘ท๐‘น โŠฅ ๐‘ด๐‘ธ . Assume that there is another line ๐‘ท๐‘บ โŠฅ ๐‘ด๐‘ธ . Then by the definition of perpendicular, โˆ ๐‘บ๐‘ท๐‘ธ is a right angle and therefore ๐’Žโˆ ๐‘น๐‘ท๐‘ธ = ๐Ÿ—๐ŸŽ. This contradicts the Angle Construction Postulate. Since the assumption leads to contradiction of postulate, it must be false. Therefore, there is only one line ๐‘ท๐‘น โŠฅ ๐‘ด๐‘ธ . R S M P Q Given: MQ and point P on MQ Prove: a. There is at least on line PR โŠฅ MQ b. There is only one line PR โŠฅ MQ
  13. 13. ๐‘ป๐’‰๐’†๐’๐’“๐’†๐’Ž ๐Ÿ’๐Ÿ There is one and only one line perpendicular to a given line through an external point. For Example: ๐ผ๐‘› ๐‘กโ„Ž๐‘’ ๐‘“๐‘–๐‘”๐‘ข๐‘Ÿ๐‘’, ๐‘๐‘œ๐‘–๐‘›๐‘ก ๐‘€ ๐‘™๐‘–๐‘’๐‘  ๐‘œ๐‘› ๐ป๐ท, ๐‘กโ„Ž๐‘’ ๐‘๐‘–๐‘ ๐‘’๐‘๐‘ก๐‘œ๐‘Ÿ ๐‘œ๐‘“ โˆ ๐พ๐ป๐‘. If ๐พ๐ป = 4๐‘ฅ โˆ’ 15 and ๐‘๐ป = 2๐‘ฅ + 3. Find ๐‘๐ป. SOLUTION: ๐‘ฒ๐‘ฏ = ๐‘ต๐‘ฏ 4๐‘ฅ โˆ’ 15 = 2๐‘ฅ + 3 Substitute the value of ๐พ๐ป and ๐‘๐ป. 4๐‘ฅ โˆ’ 2๐‘ฅ = 3 + 15 Combine similar terms. 2๐‘ฅ = 18 Simplify. 2๐‘ฅ 2 = 18 2 Divide both side by 2. ๐‘ฅ = 9 ๐‘๐ป = 2๐‘ฅ + 3 ๐‘๐ป = 2 9 + 3 Substitute the value of x ๐‘๐ป = 18 + 3 Simplify. ๐‘๐ป = 21 H D N M K
  14. 14. EXAMPLE: ๐ผ๐‘› ๐‘กโ„Ž๐‘’ ๐‘“๐‘–๐‘”๐‘ข๐‘Ÿ๐‘’, ๐ท๐‘‡ ๐‘–๐‘  ๐‘กโ„Ž๐‘’ ๐‘Ž๐‘›๐‘”๐‘™๐‘’ ๐‘๐‘–๐‘ ๐‘’๐‘๐‘ก๐‘œ๐‘Ÿ ๐‘œ๐‘“ โˆ ๐‘€๐ท๐‘„. ๐‘€๐ฟ = 5๐‘ฅ โˆ’ 12, ๐‘„๐ฟ = 2๐‘ฅ + 3, ๐ท๐‘€ = 2๐‘ฆ โˆ’ 3, ๐‘Ž๐‘›๐‘‘ ๐ท๐‘„ = ๐‘ฆ + 12. Find the perimeter of ๐‘€๐ท๐‘„๐ฟ. ๐‘€๐ฟ = ๐‘„๐ฟ ๐ท๐‘€ = ๐ท๐‘„ 5๐‘ฅ โˆ’ 12 = 2๐‘ฅ + 3 2๐‘ฆ โˆ’ 3 = ๐‘ฆ + 12 5๐‘ฅ โˆ’ 2๐‘ฅ = 3 + 12 2๐‘ฆ โˆ’ ๐‘ฆ = 12 + 3 3๐‘ฅ = 15 ๐‘ฆ = 15 ๐‘ฅ = 5 ๐‘€๐ฟ = 5๐‘ฅ โˆ’ 12 ๐‘„๐ฟ = 2๐‘ฅ + 3 ๐ท๐‘€ = 2๐‘ฆ โˆ’ 3 ๐ท๐‘„ = ๐‘ฆ + 12 ๐‘€๐ฟ = 5 5 โˆ’ 12 ๐‘„๐ฟ = 2(5) + 3 ๐ท๐‘€ = 2(15) โˆ’ 3 ๐ท๐‘„ = 15 + 12 ๐‘€๐ฟ = 25 โˆ’ 12 ๐‘„๐ฟ = 10 + 3 ๐ท๐‘€ = 30 โˆ’ 3 ๐ท๐‘„ = 27 ๐‘€๐ฟ = 13 ๐‘„๐ฟ = 13 ๐ท๐‘€ = 27 Since, we are looking for the perimeter of ๐‘€๐ท๐‘„๐ฟ. Just add the length of the sides that we get. ๐‘ƒ = ๐‘€๐ฟ + ๐‘„๐ฟ + ๐ท๐‘€ + ๐ท๐‘„ ๐‘ƒ = 13 + 13 + 27 + 27 ๐‘ƒ = 80 T L D Q M

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