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7-7 6 th grade math. Triangles. Objective. To classify and draw triangles, and find missing angles in triangles. Why? To further your knowledge in measurement and geometry and keeping building a strong foundation in MG in HS. California State Standards.
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7-76th grade math Triangles
Objective • To classify and draw triangles, and find missing angles in triangles. • Why? To further your knowledge in measurement and geometry and keeping building a strong foundation in MG in HS
California State Standards MG 2.3: Draw … triangles from information about them (e.g., … a right isosceles triangle). AF 1.1 : Write and solve one-step equations in one variable. AF 3.2: Express in symbolic form simple relationships arising from geometry MG 2.0: Identify and describe the properties of two-dimensional figures. MR 2.4: Use a variety of methods, such as words, numbers, symbols, charts, graphs, tables, diagrams, and models, to explain mathematical reasoning.
Vocabulary • Triangles • 3 sided figure and the sum of the angles are 180°. Remember that a triangle is ½ a square or rectangle (whose angles measure 360°). • Congruent triangles • Triangles with the same size and shape
Vocabulary • Equilateral triangle • A triangle with all three sides congruent • Scalene triangle • A triangle with no sides congruent (all 3 sides are different) • Isosceles triangle • A triangle with 2 sides congruent sides • Right triangle • A triangle with a right angle (only 1 angle is needed)
Vocabulary • Acute triangle • A triangle with all three angles with acute measures • Obtuse triangle • A triangle with an obtuse angle (only 1 angle is needed) ↓
Classifying Triangles Classified by Sides *Three congruent sides - equilateral triangle *Two congruent sides - isosceles triangle - may be acute, right, or obtuse *No congruent sides - scalene triangle -may be acute, right, or obtuse Classified by Angles *All acute angles - acute triangle - may be equilateral, isosceles, or scalene *One right angle - right triangle - may be isosceles or scalene *One obtuse angle - obtuse triangle -may be isosceles or scalene
How to Find Missing Angles of a Triangle 1) Add the 2 known angles 2) Subtract 180 from Step 1 3) Check work Triangle with known sides 90° and 30°. 90°+ 30° = 120° 180° – 120° = 60° 3rd side = 60°
Try It! Classify each triangle in 2 ways 1. 2. 3. 4. • Scalene, right • Isosceles, acute • Scalene, obtuse • Equilateral, acute
Try Some More! Find the m∠ of the third angle of teach triangle 5) ∠’s: 98°, 40°, ___ 6) ∠’s: 29°, 84°, ___ 7) ∠’s: 72°, 46°, ___ 8) ∠’s: 43°, 25°, ___ 5) 180 – (98 + 40) = 42° Scalene, obtuse 6) 180 – (29 + 84) = 67° Scalene, acute 7) 180 – (72 + 46) = 62° Scalene, acute • 180 – (43 + 25) = 112° Scalene, obtuse
Objective Review • To classify and draw triangles, and find missing angles in triangles. • Why? You have furthered your knowledge in measurement and geometry and keeping building a strong foundation in MG in HS • You can classify and draw triangles according to side and angle measures. By knowing that the sum of the angles of a triangle is 180°, you can find the measure of an unknown angle.
Independent Practice • Complete problems 10-23 • Copy original problem first. • Show all work! • If time, complete Mixed Review: 24-30 • If still more time, work on Accelerated Math.