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. Equilateral Triangles Figure 1 Recall the wellknown theorem of van Schooten Theorem 1 If ABC is an equilateral triangle and is a point on the arc BC of ABC then MA MB MC Proof Use Ptolemy on the cyclic quadrilater 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. Symmetry. The image is exactly the same on both sides… therefore it is reflected across the line of symmetry.. WARM UP:. Draw lines of Symmetry for the shapes on the worksheet. MOST lines of Symmetry. Geometry Module 3-1 Isosceles Right Triangle Reflections Overview: of squares through isosceles right triangles. Objective: TExES Mathematics Competencies III.012.D. The beginning teacher uses proper Sec: 4.6. 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. Leg. th. Grade. TRIANGLES. Triangles. A polygon with three sides. Is the simplest of the polygons. Formed by three straight lines. The interior angles add up to 180 degrees. Exterior angles add up to 360 degrees.. Triangles. L.E.Q. How do you use and apply properties of isosceles triangles to solve problems. ?. Parts of an Isosceles Triangle. .. Between the 2 legs.. Surround the base.. If 2 sides of a triangle are congruent, then the angles opposite those sides are congruent.. 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 . and. . 4.2/1-10. Lessons 4.1 and 4.2 . Triangle Sum Properties & Properties of Isosceles Triangles. -. Classify triangles and find measures of their angles.. - Discover the properties of Isosceles Triangles.. 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.).. Recall that an isosceles triangle has at least two congruent sides. The congruent sides are called the . legs. . The . vertex angle. is the angle formed by the legs. The side opposite the vertex angle is called the . 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..