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February 2012: triangle puzzle, Vi Hart & mathematical doodling, compound interest, geometry videos, and more

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(easy hangman)
(difficult)

The ideas in this geometry lesson are taken from the Geometry ebook that I sell at MathMammoth.com. This lesson plan does not contain all the problems the Geometry ebook does.

Polygons
Free geometry lesson plan from HomeschoolMath.net

Polygons are closed figures that have several line segments and angles
(Poly = many; gonia = angle).

Triangles are polygons with three sides.

Quadrilaterals are polygons that have four sides (quattuor = four, lateralis = side).
Some of the quadrilaterals are so special that they have they own names.
Can you spot out the special ones from amongst these quadrilaterals?

Parallelograms
have their opposite
sides parallel.

In rectangles
all the angles are
right angles.

A square has four
right angles and all
sides are equal.

This is just a quadrilateral;
nothing special about it.

Other polygons include

Pentagons have 5 sides and 5 angles
(pente = five, gonia = angle).

Hexagons have 6 sides and 6 angles
(hex = six).

Heptagons have 7 sides (hepta = seven).

Octagons have 8 sides (okto = eight).

Example problem types

1. a) Draw four dots on paper at random so that connecting them you will get a quadrilateral that is not a square, rectangle or parallelogram.
b) Measure the angles of your quadrilateral. What is the sum of the angles?
c) Draw a diagonal into it so that it divides it into two triangles. Using the triangles explain why the sum of the angles in a quadrilateral has to be what it is.

3. A regular hexagon is a hexagon whose all sides and angles are equal. Look at the pictures to learn how to construct a regular hexagon. Then draw one in your notebook using compass and ruler.


Draw an equilateral triangle with the usual method and also another triangle under- neath it.	Extend the sides of the triangles until they meet the circumference of one of the citrcles.	Connect the points where the extended lines met the circumference, and you get a regular hexagon.

5. A regular pentagon is a pentagon whose sides and angles are equal. Each angle of a regular pentagon is 108 degrees. Using that fact draw one. You can choose the length of the side.

New terms to remember:

polygon
quadrilateral
pentagon
hexagon

heptagon
octagon
regular pentagon
regular hexagon

Next geometry lesson

New! Times Tales is now on DVD!

The fast, FUN, and easy way to learn multiplication. Learn the upper times tales in two sittings using mnemonic stories.

Polygons Free geometry lesson plan from HomeschoolMath.net

Example problem types

Polygons
Free geometry lesson plan from HomeschoolMath.net