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Homework: 1.5/1-14, 17-21, 24-26 Quiz Friday on Lesson 1.3 – 1.5 To assume something is to accept it as true without facts or proof. When looking at a diagram, be careful not to assume anything Lines are straight If two lines intersect, they intersect at one point Points on a line are collinear All points shown in a diagram are coplanar unless additional planes are shown Just because they look: parallel › two lines or segments are NOT necessarily parallel perpendicular › two lines are NOT necessarily perpendicular Congruent › pairs of angles, segments, or polygons are NOT necessarily congruent All CONGRUENT, PARALLEL, PERPENDICULAR parts MUST be MARKED A triangle has three sides and three angles The three angles always add to 180° There are special names given to triangles that tell how many sides or angles are equal. There can be 3, 2 or no equal sides/angles: › Sides: Equilateral, Isosceles and Scalene › Angles: Acute, Right, Obtuse, and Equiangular Equilateral Triangle Three equal sides Isosceles Triangle Two equal sides Scalene Triangle No equal sides Acute Triangle All angles are between 0°and 90° Right Triangle Has exactly one right angle (=90°) Obtuse Triangle Has one angle between 90° and 18 Equiangular Triangle Three equal angles, always 60° Sometimes a triangle will have two descriptive names. One for angles & one for sides For example: Right Isosceles Triangle › It has a right angle (90°), and also two equal angles Can you guess what the measure of the equal angles are? YES Scalene right triangle? NO Obtuse acute triangle? Equiangular scalene triangle? NO YES Isosceles right triangle? NO Equilateral obtuse triangle? Sketch › To create the picture with only a pencil; freehand Draw › To use measuring tools: ruler and protractor Construct › To use construction tools: compass and straightedge These terms will determine what tools, if any, you are required/allowed to use. 1. 2. M 1. N A 2. O P Y U 3. 4. ΔBAD with BA = 2.5 cm, m<A = 75˚ Right scalene ΔHOP with right angle P, PO = 4cm, PH = 2cm. D 3. B 4. 75˚ 2.5cm A H 2cm P 4cm O