RETEACHING 7-11.Sample answers: XZ, WZ, WX, XY, YZ, ZM, or MX

2.M, W, X, Y or Z

3.WX and XY, WZ and ZY

4.WZ and XY

5.A. parallel 5b. Intersecting

6. A B

7.B C

RETEACHING 7-2

1.146°; obtuse

2.34°; acute

3.50°; acute

4.90°; right

RETEACHING 7-3

1.Scalene; obtuse

2.Equilateral; acute

3.Isosceles; right

4.Scalene; obtuse

5.scalene; acute

6.Isosceles; acute

7.X=105°

8.X=34°

What is a Polygon????

Any ideas?Write down what you think it is for #1.

POLYGONSExploring

WHAT IS A POLYGON?

Polygons are many-sided figures, with sides that are line segments. Polygons are named according to the number of sides and angles they have. Can be “regular” – all sides and all angles are equal to each other

ISOSCELES TRIANGLES

Two sides of equal lengthThree acute anglesSum of angles = 180°

Hint: Think “Tri”cycle, “tri”pod, “Tri”lateration (Tri means 3)

EQUILATERAL TRIANGLES

All sides equal lengthThree acute angles Sum of angles = 180°Is a regular polygon

SCALENE TRIANGLES

No sides are equalNo angles are equalMay have obtuse angleSum of angles = 180 °

Classifying Polygons by # of Sides

4 sided Polygon = Quadrilateral

Hint: Think “Quad”rant, “Quad”ruple, “Quad” (AKA 4-Wheeler)

RECTANGLES

Opposite sides are parallelOpposite side are equal in lengthEach angle equals 90°Sum of angles = 360°

SQUARES

All sides equalAll angles equal and are 90 ° eachSum of angles = 360 °Is a regular polygon

TRAPEZOIDS

Two sides are parallelHas obtuse and acute anglesSometimes has a right angleSum of angles = 360 °

RHOMBUSES (RHOMBI)

All four sides of equal lengthOpposite angles are equal – 2 acute angles, 2 obtuse anglesSum of angles = 360 °Regular polygon

PARALLELOGRAMS

Opposite sides parallelOpposite sides equal in lengthOpposite angles equalSum of angles = 360 °

PENTAGONS

5 sides Sum of

angles = 540 °

Regular polygon

Hint: Think “Pent”athalon, or the government building “The Pentagon”

HEXAGONS

6 sides Sum of angles =

720 ° Can be regular

polygon

Hint: Both “Hexagon” and “Six” have an ‘x’ in them

OCTAGONS

8 sides Sum of angles =

1080 ° Can be regular

polygon

Hint: “oct”opus – 8 legs

DECAGONS

10 sides Sum of angles =

1440° Can be regular

polygon

Sum of angles in a REGULAR POLYGON:

(n-2)180

Remember n=number of sides

Each interior angle in a regular polygon:

(n-2)180/n

REGU LAR PO LYGO N: INTERIO R ANG LE SU M

REGULAR HEXAGON

INT ANGLE SUM =(6 – 2 ) 180 = 720°

EACH INT ANGLE = 720 = 120°

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