PPT-4.8: Isosceles & Equilateral Triangles

Objective To understand and apply properties of isosceles and equilateral triangles Supplies Math Notebook Assignment 48 p 276 110 1216 2226 48 Isosceles amp Equilateral Triangles. Congruent Triangles. Dr J Frost (jfrost@tiffin.kingston.sch.uk. ). www.drfrostmaths.com. . Last modified: . 31. st. August 2015. Associated Resources: GCSEQuestions-Congruence.doc. GCSE Revision Pack Refs: 169, 170. Classifying Triangles by Angles. ACUTE. OBTUSE. RIGHT. EQUIANGULAR. ACUTE TRIANGLE. All interior angles are acute (or have a measure less than 90°). Interior Angle. Example of Acute Triangle. Phineas’s. Sec: . 4.5. Sol: G.5. Properties of Isosceles Triangles. An isosceles triangle is a triangle with two congruent sides.. The congruent sides are called legs and the third side is called the base.. 3. “. Cogito ergo sum.”. -- Rene Descartes, . Discourse on the Method. . real mathematics. “Mathematics. , rightly viewed, possesses not only truth, but supreme beauty—a beauty cold and austere, like that of sculpture, without appeal to any part of our weaker nature, without the gorgeous trappings of painting or music, yet sublimely pure, and capable of a stern perfection such as only the greatest art can show. 4.2. SSS Postulate (Just call it SSS). If . three sides of one triangle . are congruent to. three sides of another triangle, . then the triangles are congruent.. SAS Postulate (Just call it SAS). If . A. . = . B. . C. . D. . = .  . Warm-Up. ~Write one sentence explaining what answer you chose.. ~Write one sentence explaining what answers you were able to eliminate.. Polygons and Triangles. The word polygon means many (poly) angles (gon). This includes triangles, squares, rectangles, trapezoids, parallelograms, . Helpful websites. http://www.regentsprep.org/Regents/mathb/1c/preprooftriangles.htm. http://www.mathwarehouse.com/geometry/congruent_triangles/. http://www.cliffsnotes.com/WileyCDA/CliffsReviewTopic/Congruent-Triangles.topicArticleId-18851,articleId-18788.html. Triangles. Isosceles Triangles. leg. leg. base. Vertex angle. Base angle. Base angle. 2 sides are congruent. 2 theorems. If 2 sides are congruent, then base angles are congruent. If 2 . base angles . Warm Up. 1. . Find each angle measure.. True or False. If false explain.. 2.. Every equilateral triangle is isosceles.. 3.. Every isosceles triangle is equilateral.. . 60°; 60°; 60°. True. False; an isosceles triangle can have only two congruent sides.. CCSS. Content Standards. G.CO.10 Prove theorems about triangles. . G.CO.12 Make formal geometric constructions with a variety of tools and methods (compass and straightedge, string, reflective devices, paper folding, dynamic geometric software, etc.).. Lewis Carroll/Charles Dodgson. Some . fun facts:. .. as a mathematician, Dodgson was, in the words of . . Peter Heath: "An inveterate publisher of trifles [who] was forever putting out pamphlets, papers, broadsheets, and books on mathematical topics [that] earned him no reputation beyond that of a crotchety, if sometimes amusing, controversialist, a compiler of puzzles and curiosities, and a busy yet ineffective reformer on elementary points of computation and instructional method. In the higher reaches of the subject he made no mark at all, and has left none since." . Chapter 4. This Slideshow was developed to accompany the textbook. Larson Geometry. By Larson. , R., Boswell, L., . Kanold. , T. D., & Stiff, L. . 2011 . Holt . McDougal. Some examples and diagrams are taken from the textbook.. Magic Triangles. There are 3 magic triangles, two of which are on your formula sheet. They let you do some trigonometric equations without calculators. These are a fundamental part of ”exact solutions” . Geometry. Legs are congruent. Isosceles Triangle. Vertex Angle. Base Angles. Legs. Theorem 4-3 (Isosceles Triangle . Thm. ):. If two sides of a triangle are congruent, then the angles opposite those sides are congruent..