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CCSS.Math.Content.8.G.A.5 Use Informal...

CCSS.Math.Content.8.G.A.5 - Use informal arguments to establish facts about the angle sum and exterior angle of triangles, about the angles created when parallel lines are cut by a transversal, and the angle-angle criterion for similarity of triangles. For example, arrange three copies of the same triangle so that the sum of the three angles appears to form a line, and give an argument in terms of transversals why this is so.

Authors: National Governors Association Center for Best Practices, Council of Chief State School Officers

Title: CCSS.Math.Content.8.G.A.5 Use Informal Arguments To Establish Facts About... Geometry - 8th Grade Mathematics Common Core State Standards

Publisher: National Governors Association Center for Best Practices, Council of Chief State School Officers, Washington D.C.

Copyright Date: 2010

(Page last edited 10/08/2017)

  1. A Mathematical Droodle - Two Triples of Similar Triangles
  2. Connecting Geometry: Similar Triangles - Similar triangles can be very useful for measuring inaccessible objects. One method of doing this is called "shadow reckoning," which this page describes
  3. Examples of SSS, SAS, and AA - From Yahoo Answers
  4. GeoWeb - Proving Triangles Similar and Congruent
  5. Indirect Measurement with Similar Triangles - This five page lesson plan describes how to use a mirror in making indirect measurements.
  6. Math Open Reference: Similar Triangles - Interactive triangle lesson
  7. Measuring Angles - Use a virtual protractor
  8. Proof Using Similar Triangles - Four examples to print and use in your classroom (text document)
  9. Proportionality in Similar Triangles: A Cross-Cultural Comparison - A lesson plan from Convergence: a magazine of the Mathematical Association of America
  10. Similar Triangles - Explanation of the concept
  11. Similar Triangles - Includes the AA rule and the RAR rule plus two videos
  12. Similar Triangles - A 23 slide PowerPoint show which includes scaling factors
  13. Similar Triangles and Indirect Measurement - This worksheet gives a short review, an example and five practice problems
  14. Similar Triangles and the Pythagorean theorem - From Dave's Short Trig Course
  15. Similar Triangles II - A 14 slide PowerPoint show
  16. Similar Triangles: SAS, AA, SSS - Theorems that prove triangles are similar
  17. Strategies for Dealing with Similar Triangles - From Oswego City School District Regents Exam Prep Center [from the Internet archive, called the Wayback Machine.]
  18. Sum of Angles in a Triangle - Students can explore this concept by moving the vertices of the triangle with pressed mouse button
  19. Three Similar Triangles - A math droodle
  20. Triangle Calculator - Enter values three of the six sides and angles of the triangle and the other three values will be computed. The number of significant values entered will determine the number of significant figures in the results.
  21. Understanding Scale Factors - Similar Triangles: Perimeters and Areas - When two triangles are similar, the reduced ratio of any two corresponding sides is called the scale factor of the similar triangles



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