### Circle Circle Circle

ACTIVITY 3A

Post your responses of the following:

• Why is a circle a 'circle' and why it is NOT a triangle?   Describe its characteristics.
• Give at least 2 examples of daily objects, figures, shapes that could be classified as a circle.

1. cir·cle
ˈsərkəl/

noun

a round plane figure whose boundary (the circumference) consists of points equidistant from a fixed point (the center).

versus

tri·an·gle
ˈtrīˌaNGgəl/

noun

a plane figure with three straight sides and three angles.

The two are fundamentally different. A circle is made up of points equidistant from the centre whereas a triangle is made up of three points, not always equidistant from the center, connected.

- Balram, Darryl and Hao Xian

1. Your definition is concise, yet it explains most properties of the circle. However, there are other ways to express the same concepts, such as describing a circle as a shape with infinite sides.

2. -It has fixed diameter (It is the shape formed by radii from the center)
It is an infinite sided square.

1. What do you mean by fixed diameter? Only circles with a certain diameter are circles?

2. its not an infinite sided square its an infinite side polygon.

3. Bacteria colonies are, at most, hemispheres.

4. - A square has four sides; "an infinite-sided square" is pretty much contradictory
- A square has 4 right angles, circles do not have such things

— Charlene and Aziel

5. isn't an infinite sided square an infinite sided polygon?

3. 1. There's no point in the circle and radius is equidistant from the centre. Circle has no vertices while triangle have three vertices.

2. Pancake, frisbee, pizza, CD, plates.

Done by Kai Chek, Jun Jie and Jee Hoon

4. A circle's center-point is always equidistant from its circumference.
A triangle has interior angles that adds up to 180 degrees while circle has no interior angles
Circular Wall Clock
Circular table
50cents coins

1. Your examples are all cylinders.

The "spinning beach ball of death" - http://www.mixcrate.com/img/ugc/covers/1/7/174702_l.jpg?v=709201223

A typical jet engine - http://www.bloomberg.com/image/ihDojHjwKtvs.jpg

6. A circle is a 'circle' because every point on a circle is the same distance from the center.

Examples of daily objects that could be classified as a circle: Frisbee, Ball

1. How is the circle different from a triangle?
A ball is not a circle, but a sphere.

2. Very vague explanation of circle. The question is to explain what is circle, but answering it saying circle is "circle".... is just repeating the question itself again.

7. The definition of a circle is a curved line that is the same distance from the center all the way around and connects at the point where it began.

An object with infinite sides.

Symmetrical from all sides
CDs and 360˚ Protractors

8. A circle is a 2 dimensional shape in which any point on the circumference is equidistant to the centre

Examples of a circle
- CD disc

— Aziel and Charlene

9. 1. There's no point in the circle and radius is equidistant from the centre. Circle has no vertices while triangle have three vertices.

2. Pancake, frisbee, pizza, CD, plates.

Done by Kai Chek, Jun Jie and Jee Hoon

1. Define "point in a cricle"

10. Properties of a circle:
1. A circle has infinite points
2. A circle does not have parallel lines
3. The area of a circle can be defined as πr^2
4. Any line from the centre of the circle to the circumference is equal
5. All circles are similar

Examples:
1. The buttons on Mr Johari's shirt
2. Manholes
3. Cross-section of a stem
4. The SST sticker
5. Pupil (Eye)

1. How is the circle different from other shapes such as the triangle?