Angles and Triangles Terry Scates Newton, Kansas

Instructor Notes Subject Area(s): Math Grade level: 7 th grade Lesson Length: 50 minute class period Synopsis: Name triangles by angles and sides. Objective/goals: Students will classify triangles according to types or angles and sides. (This PowerPoint presentation was designed as a supplemental piece to the presentation entitled Classifying Triangles by James Wiens for students in the special education math class.)

Standard: ▲ identifies angle and side properties of triangles and quadrilaterals (KS standard k3) Pre-requisite skills: Vocabulary – Acute, Obtuse, Right, Equilateral, Isosceles, Scalene TurningPoint functions: standard question slides Materials: All instructional points and practice problems are provided within the power point slides. Practice questions are designed to be used with the TurningPoint clickers. (This PowerPoint presentation was designed as a supplemental piece to the presentation entitled Classifying Triangles by James Wiens for students in the special education math class.) Instructor Notes

Lesson Outline 1.Warm-up: Angle classification 2.Setting the Stage: 3.Guided practice: Turning Point Questions 4.Independent practice: Paper & pencil 5. Closure: Write about triangles

What we already know about angles : An angle has two sides that share a common endpoint.

What we need to know about angles : The point where the sides meet is called the vertex.

What we need to know about angles : Angles are measured in degrees, where 1 degree is one of 360 equal parts of a circle.

Angles are classified according to their measure. An acute angle is less than 90° An obtuse angle is more than 90° A right angle is 90°

Right Angle Find some examples of right angles in the classroom:

Acute Angle Find some examples of acute angles in the classroom:

Obtuse Angle Find some examples of obtuse angles in the classroom:

Classify this angle: a)Acute b)Right c)Obtuse Classify this angle: Countdown 10

Classify this angle: a)Acute b)Right c)Obtuse Countdown 10

Classify this angle: a)Acute b)Right c)Obtuse Countdown 10

What we already know about triangles: A triangle is a figure with three sides and three angles. The symbol for triangle is

What we need to know about triangles: The sum of the measures of the angles of a triangle is 180°. You can use this to find a missing angle measure in a triangle.

Triangles can be classified by the measures of their angles.

An acute triangle has three acute angles.

An obtuse triangle has one obtuse angle.

A right triangle has one right angle.

Triangles can also be classified by the lengths of their sides.

Sides that are the same length are congruent segments and are often marked by tick marks.

In a scalene triangle, all sides have different lengths.

An isosceles triangle has at least two congruent sides.

An equilateral triangle has all three sides congruent.

Classify this triangle by angles and by sides 1.Acute / Isosceles 2.Obtuse / Isosceles 3.Acute / Scalene 4.Obtuse / Scalene Countdown 10

Classify this triangle by angles and by sides Acute / Isosceles 2.Right / Isosceles 3.Acute / Scalene 4.Right / Scalene Countdown 10

Classify this triangle by angles and by sides 1.Acute / Isosceles 2.Obtuse / Isosceles 3.Acute / Scalene 4.Obtuse / Scalene Countdown 10

Classify this triangle by angles and by sides Acute / Isosceles 2.Right / Isosceles 3.Acute / Equilateral 4.Obtuse / Scalene Countdown 10

You are ready to try on your own! Think about what you have learned. Think about what you already knew. Think about what you can teach others.

Independent Practice

Answer Key for Independent Practice A.Obtuse / Isosceles B.Acute / Equilateral C.Right / Isosceles D.Acute / Isosceles E.Obtuse / Isosceles F.Acute / Equilateral G.Obtuse / Scalene H.Right / Scalene

Closure/Summary Is the sum of the angles of an obtuse triangle greater than the sum of the angles of an acute triangle? Explain your answer.

References Glencoe McGraw-Hill Math Connects Course 2, Study Guide and Intervention and Practice Workbook, Wiens, James, Classifying Triangles, PowerPoint presentation, November 2008.