The document defines a circle and its key properties. A circle is a closed loop where every point is equidistant from the center point. The center is at the innermost point, and the radius extends from the center to any point on the circle. The diameter stretches across the circle by going through the center. Other aspects are chords (lines between two circle points), tangents (lines touching at one point), and secants (lines intersecting at two points). Formulas are provided for calculating circumference and area based on radius and diameter. Examples are given for using the formulas and drawing circles with compasses.

1. Circles
By: Javent Erl Cadalso

2. What is circle?
 A line forming a closed loop, every
point on which is a fixed distance from
a center point.
 The word "circle" derives from the
Greek, kirkos "a circle," from the base
ker- which means to turn or bend.

3. Properties of a circle
 Center A point inside the circle. All points on
the circle are equidistant (same distance)
from the center point.

4.  Radius The radius is the distance from the
center to any point on the circle. It is half the
diameter.
 Diameter The distance across the circle. The
length of any chord passing through the center.
It is twice the radius.

5.  Chord A line segment linking any two points on a
circle.
 Tangent A line passing a circle and touching it at
just one point.

6.  Secant A line that intersects a circle at two
points.

8. Formulas of circle in circumference
and area
 Circumference
 Area

9. Exercises
1. Find the circumference of a circle with a
diameter of 11 millimeters.
2. Find the diameter of a circle with a
circumference of 21.98 meters.
3. Find the area of a circle with a radius of 4
inches.
4. Find the radius of a circle with an area of
200.96 square feet.
5. If the radius of a circle is 1.5 inches, then what
is the circumference?

10. How to draw a circle
Compass
 An instrument containing a magnetized pointer that
shows the direction of magnetic north and bearings from
it.
 An instrument for drawing circles and arcs and
measuring distances between points, consisting of two
arms linked by a movable joint, one...

11. Use a compass to draw a circle
of radius 4 cm.
Step 1: Use a ruler to set the distance from the
point of the compass to the pencil's lead at 4 cm.
Step 2: Place the point of the compass at the
centre of the circle.
Step 3: Draw the circle by turning the compass
through 360º.

12. Exercises
1. Draw a circle with a circumference is
10 mm
2. Draw a circle with a diameter is
20mm
3. Draw a circle with having an area of
12cm squared
4. Draw a circle with a radius of 2mm
5. Draw a circle with having an area of
10mm squared

13. Reference
 http://en.wikipedia.org/wiki/Circle
 http://www.mathopenref.com/circle.
 www.mathsisfun.com/geometry/circle.
html
 www.math.com/school/subject3/lesson
s/S3U1L6GL.html
 www.circles.com/

14. Thank you for listening. .