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 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 ° 3 rd side = 60 °

Try It! Classify each triangle in 2 ways )Scalene, right 2)Isosceles, acute 3)Scalene, obtuse 4)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 – ( ) = 42 ° Scalene, obtuse 6) 180 – ( ) = 67 ° Scalene, acute 7) 180 – ( ) = 62 ° Scalene, acute 8)180 – ( ) = 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 Copy original problem first. Show all work! If time, complete Mixed Review: If still more time, work on Accelerated Math.