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Triangles

Today our focus was on the six types of triangles. Our learning goal was to identify the types of triangles (acute, obtuse, right, equilateral, isosceles and scalene) by looking at the angles and side attributes. I got the idea for this activity from Interactive Math Journal from Runde's Room.

To begin, I did another formative assessment with the classes. This time the assessment is called "Always, Sometimes, Never." I found this assessment idea in the book, Mathematics Formative Assessment by Page Keeley and Cheryl Rose Tobey. Using Kahoot, the students were presented with 11 statements about triangles. They needed to think about what they already knew about triangles and use this information to help them to choose "always, sometimes, or never" . The eleven statements are below:

- Triangles are named by their angles.
- Triangles are named by the number of congruent sides.
- A right triangle has two right angles.
- An acute triangle has all acute angles.
- An obtuse triangle has three obtuse angles.
- An equivalent triangle has 3 congruent sides and angles.
- A triangle can have two names.
- An isosceles triangle is named for its two congruent sides.
- A scalene triangle is named for its angles.
- The angles within a triangle measure 180 degrees.
- A triangle is the most stable shape.

Next, I handed each student a sheet of paper with six triangles on them. We numbered the triangles and cut them apart in two long strips so that I did not have to spend much class time cutting apart six triangles! We taped the strips into our journal and then took notes about each one. We began by breaking the triangles into two groups (1) those that are named for their angles and (2) those that are named for the number of congruent sides. By the end of the note taking, I wanted the kids to understand that triangles have two names. They have a name for their angles AND a name for their sides (i.e. right, scalene triangle or acute, equilateral triangle, etc.)

Once we had taken the notes, we revisited our formative assessment page to discuss how we would answer the statements now:

- Triangles are named by their angles: Sometimes (acute, obtuse, right)
- Triangles are named by the number of congruent sides: Sometimes (equilateral, isosceles, scalene)
- A right triangle has two right angles: Never
- An acute triangle has all acute angles: Always
- An obtuse triangle has three obtuse angles: Never
- An equivalent triangle has 3 congruent sides and angles: Always
- A triangle can have two names: Always (one for the angles AND one for the sides)
- An isosceles triangle is named for its two congruent sides. Always
- A scalene triangle is named for its angles: Never (it is named for its sides)
- The angles within a triangle measure 180 degrees: Always
- A triangle is the most stable shape: Always

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