Circles

From Karnataka Open Educational Resources

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Concept Map

Additional Resources[edit | edit source]

OER[edit | edit source]

  1. Web resources :
    1. maths is fun A good website on definitions for circles.
    2. Cool math For clear and easy definitions.
    3. Open reference Contains good simulations.
    4. Wikipedia Has good explanations on circles.
    5. Khan academy Has good educative videos.
    6. Arvind gupta toys Contains good information.
    7. nrich.maths.org Refer for understanding Pi.
  2. Books and journals
    1. School Geometry By Hall and Stevens. Part3 pageno 143. Contains basic definitions and proofs given by Euclid.
  3. Textbooks:
    1. Class 9 Mathematics contain simple description and theorems on circle
    2. CLASS 10
  4. Syllabus documents

Non-OER[edit | edit source]

  1. Web resources

 : This is a resource file created by Suchetha, Mathematics teacher, GJC Thyamangondlu

    • This is a video showing construction of tangent from external point and theorem

 : This is a resource file created by Suchetha, Mathematics teacher, GJC Thyamangondlu

      • you want see the kannada videos on theorems and construction of circle click here this is shared by Yakub koyyur GHS Nada.
  1. Books and journals
  2. Textbooks
    1. Karnataka text book for Class 10, Chapter 14 - Chord properties
    2. Karnataka text book for Class 10, Chapter 15 - Tangent Properties
  3. Syllabus documents (CBSE, ICSE, IGCSE etc)

Learning Objectives

  • Appreciation of circle as an important shape as it is an intrical component in the invention of almost everything that we see around us.
  • To make students know that circle is a 2-dimensional plane circular figure.
  • All points on its edge are equidistant from the center.
  • The method of drawing a circle
  • The size of the circle is defined by its radius.
  • To elicit the difference between a bangle or a circular ring and circle as such.

Teaching Outlines

Concept #1 Introduction to Circle

Source: http://circlesonly.wordpress.com/tag/inventions/
Summary : The circle is the most primitive and rudimentary of all human inventions, and at the same time, the most dynamic. It is the cornerstone in the foundation of science and technology. It is the basic tool of all engineers and designers. It is used by the greatest artists and architects in the history of mankind. Without a circular shape the wheel, pulleys, gears, ball bearings and a thousand other items we take for granted wouldn’t exist. And of course we would never have the pleasure of driving a car, riding a giant wheel, or watching the moon landing on our television set.
If you look through any old patent claim, you will most likely find the repeated use of circles, spheres, curves, arches, etc. circles are everything and they are nothing. They don’t exist in reality and yet they are the basis of all that mankind has brought into existence. That is why a circle is so fantastic.

Activities
A discussion on “Life without circular shaped figures.”
Circle as a shape
Pi the mathematical constant
Is circle a Polygon ? - A debate
Concentric circles
Congruent circles
Equal parts in a circle

Concept #2 Terms associated with circles

Activities
Centre of a circle
Radius and diameter of a circle
Circumference of a circle
Semicircle
Interior and exterior of a circle
Basic elements of a circle
Chord of a circle
Arc of a circle

The part of the circumference within the two points in either directions are called its arcs.

Sector of a circle

Concept #3: Circles and Lines

Activities
Introduction to chords
Secant and tangent of a circle
Concept #4: Theorems and properties

A chord is a straight line joining 2 points on the circumference of a circle.Chords within a circle can be related in many ways.

The theorems that involve chords of a circle are :

  • Perpendicular bisector of a chord passes through the center of a circle.
  • Congruent chords are equidistant from the center of a circle.
  • If two chords in a circle are congruent, then their intercepted arcs are congruent.
  • If two chords in a circle are congruent, then they determine two central angles that are congruent.
Activities
Chord length and distance for centre of the circle
The longest chord passes through the centre of the circle
Perpendicular bisector of a chord passes through the center of a circle
Congruent chords are equidistant from the center of a circle
Angles in a circle subtended by a chord

Concept #5: Cyclic Quadrilateral

A quadrilateral ABCD is called cyclic if all four vertices of it lie on a circle.In a cyclic quadrilateral the sum of opposite interior angles is 180 degrees.If the sum of a pair of opposite angles of a quadrilateral is 180, the quadrilateral is cyclic.In a cyclic quadrilateral the exterior angle is equal to interior opposite angle.

Activities
Cyclic quadrilateral
Properties of cyclic quadrilateral

Concept #6 Constructions in circles

The students should know that tangent is a straight line touching the circle at one and only point.They should understand that a tangent is perpendicular to the radius of the circle.The construction protocol of a tangent.Constructing a tangent to a point on the circle.Constructing tangents to a circle from external point at a given distance.A tangent that is common to two circles is called a common tangent.A common tangent with both centres on the same side of the tangent is called a direct common tangent.A common tangent with both centres on either side of the tangent is called a transverse common tangent.

Activities
Construction of direct common tangent
Construction of transverse common tangent
Construction of cyclic quadrilateral
Solved problems/ key questions (earlier was hints for problems).

Projects (can include math lab/ science lab/ language lab)

  1. Collect different types of circular objects
  2. Collect different Pie Charts.
  3. Collect different photographs of tools of cutting circles
  4. Collect different coins of circular shape
  5. Collect different images of medals

Assessments - question banks, formative assessment activities and summative assessment activities