What’s Up With Triangles?

Math LollapaloozaMay 7, 2013

Presented byMary Alice Hatchett, President of TCTM

A treasure trove of triangles

How many triangles?

A treasure trove of trianglesNCTM article from January 2010 journal ‘Teaching Children Mathematics’

Triangles in the REAL World

Triangle Vocabulary

TRIANGLE

a closed shape formed by connecting three line segments.

Triangle Vocabulary

EQUILATERAL TRIANGLE

a triangle with all three sides congruent and all angles measuring 60 degrees

CLASSIFIED BY SIDE LENGTH

Triangle Vocabulary

SCALENE TRIANGLE

a triangle with no congruent sides or congruent angles.

CLASSIFIED BY SIDE LENGTH

Triangle Vocabulary

ISOSCELES TRIANGLE

a triangle with two congruent sides and congruent angles opposite the congruent sides

CLASSIFIED BY SIDE LENGTH

Triangle Vocabulary

RIGHT TRIANGLE

a triangle that has one 90 degree angle

CLASSIFIED BY ANGLE MEASURE

Triangle Vocabulary

ACUTE TRIANGLE

all angles in the triangle are less than 90 degrees

CLASSIFIED BY ANGLE MEASURE

Triangle Vocabulary

OBTUSE TRIANGLE

a triangle with one angle that is greater than 90 degrees

CLASSIFIED BY ANGLE MEASURE

Triangle Vocabulary

VERTEX ANGLE OF A TRIANGLE

the angle in an isosceles triangle that is not opposite a congruent side

Triangle Vocabulary

HYPOTENUSE OF A TRIANGLE

the side of a right triangle opposite the right angle; the longest side of a right triangle

Triangle Vocabulary

LEG OF A TRIANGLE

one of the sides of a right triangle that is not the hypotenuse.

Triangle Vocabulary

ALTITUDE OF A TRIANGLE

a line segment that goes from a vertex to the opposite side (BASE) forming a right angle ( also known as HEIGHT)

Triangle Vocabulary

BASE ANGLES OF A TRIANGLE

two congruent angles that are opposite the congruent sides in a isosceles triangle

Triangle Match Up Game

You will need:• One set of game cards (shuffled) per pair of students• One game board OR the label cards

Take a minute to read the directions.

Triangle Match Up Game

Obtuse & Isosceles

Obtuse & Scalene

Right & Isosceles

Acute & Equilateral

Acute & Isosceles

Acute & Scalene

Right & Scalene

Not a triangle

Triangle Match Up Game

Between peRIMeter and Height

You need:• 6 strips of paper (about 2cm by 21 cm)• Tape• Centimeter grid paper• Centimeter ruler

Between peRIMeter and Height

Between you and your partner – build:• Fold one strip into thirds, and tape to make a triangle. Label it shape “A”• Fold the other strips into 4ths, 5ths, 6ths, 7ths, and 8ths. Label as B, C, D, E, and F.

Between peRIMeter and Height

Measure the length of 1 side of each shape and write the measurement on your shape.

ORDER:The shapes from shortest side length to longest side length.

Side length

Height

# squares

Between peRIMeter and Height

Stand each shape on 1 side.

ORDER:The shapes from shortest to tallest.

Side length

Height

# squares

Measure the height of each shape and write the measurement (h=___) on the back of the side length.

Between peRIMeter and Height

Lay your shapes FLAT on the grid paper. Carefully trace around each shape.

COUNT:The number of square units inside your shape. Record your count on the grid AND record the shape ID.

CAREFULLY:Cut out each shape and order them from least number of squares to most number of squares.

Between peRIMeter and Height

Lay your shapes FLAT on the grid paper. Carefully trace around each shape.

COUNT:The number of square units inside your shape. Record your count on the grid AND record the shape ID.

CAREFULLY:Cut out each shape and order them from least number of squares to most number of squares.

Side length

Height

# squares

Are they in the same order as before?

Thank You for attending.

Don’t forget to put the AACTM Fall date on your calendar.

CAMT will be in San Antonio this summer. AACTM will get together for a ‘Happy Hour’

Mary Alice HatchettMy website: mahatchett.com

My email: mahat@earthlink.netMy store: www.teacherspayteachers.com/Store/Mary-Alice-

Hatchett

AACTM website: www.aactm.org