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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.

Circles
Free geometry lesson plan from HomeschoolMath.net

What is a circle? Discuss with your teacher.

Everybody knows
these are NOT
circles. But why?

These figures have round
shapes, but they are not
circles either. What in them
is different from circles?

These are ovals, and they are
real smoothly round but still
not circles.
So what makes a real circle?

There is a special point inside a circle called the center point. The circle line is called the circumference. All the points on the circumference are AT THE SAME DISTANCE from the center point. That is the definition of a circle: All the points that are at the same distance from a given point (center point) constitute a circle.
This distance from the center point to any point on the circumference is called the radius.		A line that crosses the circle and goes through the center point is called a diameter.

Example problem types

1. Draw a radius/diameter from the given point. Look at the example.


Here a radius is drawn from the given point.		a) Draw a radius from the given point		b) Draw a radius from each of the given points.

2. Practice drawing circles with your compass. Draw a circle with a 1 inch radius, with 5 cm radius, with 3 cm radius, with 1/2 inch radius.

3. How does the radius of the circles relate to the radius of the other circles in the pictures?
Practice drawing the figures in your notebook using compass and ruler only.

Hint: You will need to make use of the center point of the circles, so mark them down on
paper after you have drawn any circles. The circles can be bigger or smaller as you choose. The important thing is to make the pictures look the same.

5. Draw a line and then two points on the line.
Then draw a circle using one point as a center point and the other point as a marking the radius. In other words, use the distance between the two points as the radius. Now draw another circle using the second point as the center point and the first point as indicating the radius. Look at the picture.
a) Now draw a line through the points where the two circles intersect. What do you notice? b) If you connect the two initial points to the point above them where the two circles intersect (cross), what kind of figure do you get?

7. Draw an equilateral triangle with the compass and ruler only (don't use the protractor). You can choose the length of the side. Hint: the idea is the same as in problem 6.

New terms to remember:

circle
circumference

radius
diameter

Next geometry lesson

TenMarks: An affordable summer math program

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Circles Free geometry lesson plan from HomeschoolMath.net

Example problem types

Circles
Free geometry lesson plan from HomeschoolMath.net