STUDY LINK 3.8

When you are finished checking your study link; start on Math Boxes 3.8

I can find the angle measurement sum for any polygon.

3.9 ANGLES OF POLYGONS

1. Draw a large triangle on the blank piece of paper on your desk.

2. Use your protractor to measure each angle; label each angle.

3. Add the measure of the angles and record the sum on our line plot (draw

an “X” above the sum for your triangle).

MATH MESSAGE

Arrange your 3 angles next to each other so they line up.

What type of angle have you created?What does this show?

TEAR THE THREE ANGLES OFF OF YOUR TRIANGLE

DRAW EXAMPLES OF

Polygons Not Polygons

Convex Polygons Concave (nonconvex) Polygons

Groups of 4Mrs. H. will assign your group “quadrangle” or “pentagon”

JOURNAL PAGES 85-86

CLASS DATA (JOURNAL PAGES 87 & 88)

Group Group Median

Group Group Median

Quadrangles Pentagon

Why do you think the measures increase by 180°?How many degrees are in a triangle?

Quadrangles divide into _______ triangles.

DAY 2 DIVIDING POLYGONS INTO TRIANGLES

2 x 180° = 360°

**When drawing lines to divide a polygon into triangles, the lines must go from one vertex to another; they cannot start or end in the middle of the polygon or between the endpoints of the line segments.

HOW MANY TRIANGLES CAN BE DRAWN IN A PENTAGON?

3 x 180° = 540°

HOW MANY TRIANGLES CAN BE DRAWN IN A HEXAGON?

4 x 180° = 720°Conclusion: When you add another side to the figure, you are able to draw an additional triangle in the figure, which adds 180°.

What do you notice about the relationship between the number of sides of the polygon and the number of triangles that can be drawn in it? The number of triangles inside the polygon is 2 less than the number of sides.

MATH JOURNAL PAGE 89 (AND MM 94)

Name Number of sides

Equation Total Degrees

Triangle

Quadrilateral/QuadranglePentagon

Hexagon

Heptagon

Octagon

Nonagon

Decagon

Dodecagon

1. Math Journal pages 90-91; tessellations

website2. MM 93 (Left)

CENTERS

Centers

Study Link 3.9

HOMEWORK