TRIANGLES Classifying Triangles When you classify something you are assigning it to a group because it has the qualities of that group. For instance, I can classify the book "The Cat in the Hat" as Fiction because it is not true. Triangles can be classified by the length of their sides or by the measure of their angles. When classifying a triangle by its side it can either be: Equilateral: all sides of the triangle are equal in length Isosceles: two sides of the triangle are equal in length Scalene: none of the sides of a triangle are equal in length Interior Angles of a Triangle When you classify triangles by the measure of their angles they can either be: Acute Triangles: a triangle with all acute angles Right Triangles: triangles with one right angle Obtuse Triangles: triangles with one obtuse angle The interior angles of a triangle are the angles inside the shape The sum of the degrees of the interior angles of a triangle always add up to 180 degrees What is the measure of the missing angle? Side Lengths and angle measures In a triangle the sum of the length of two sides of a triangle is greater than the length of the third side. WHAT?!?! If you add the length of any 2 sides of triangle your answer will be more than the length of the other side Can you make a triangle using the following numbers for side lengths? 3, 3, 4 In any triangle: the largest interior angle is opposite the longest side

the smallest interior angle is opposite the shortest side

the mid-sized interior angle is opposite the mid-sized side http://www.mathwarehouse.com/geometry/triangles/interactive-triangle.htm Try it out!!! Yes, because 3+3=6 and 6 is more than 4

or 3+4=7 and 7 is more than 3

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# 5th Grade Triangles Lesson

Students will review how to classify triangles and will learn about the interior angles of the triangle

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