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Investigating the diameter is the longest chord of a circle.
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= Concept Map =
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===Objectives===
__FORCETOC__
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To understand longest chord passes through the centre and it is the diameter
<mm>[[circles_and_lines.mm|flash]]</mm>
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===Estimated Time===
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30 minutes
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= Textbook =
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===Prerequisites/Instructions, prior preparations, if any===
To add textbook links, please follow these instructions to:
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Prior knowledge of point, lines, angles, polygons
([{{fullurl:{{FULLPAGENAME}}/textbook|action=edit}} Click to create the subpage])
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=Additional Information=
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===Materials/ Resources needed===
==Useful websites==
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* Digital : Computer, geogebra application, projector.
#[http://www.regentsprep.org/Regents/math/geometry/GP14/PracCircleSegments.htm www.regentsprep.com] conatins good objective problems on chords and secants <br>
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* Non digital : Worksheet and pencil, compass, strings
#[http://www.mathwarehouse.com/geometry/circle/tangents-secants-arcs-angles.php www.mathwarehouse.com] contains good content on circles for different classes<br>
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* Geogebra files :  [https://ggbm.at/c4eg7q2u Diameter is longest chord.ggb]
#[http://staff.argyll.epsb.ca/jreed/math20p/circles/tangent.htm staff.argyll]  contains good simulations
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{{Geogebra|c4eg7q2u}}
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==Reference Books==
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===Process (How to do the activity)===
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Use the geogebra file to show how diameter is the longest chord.
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= Teaching Outlines
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Move the points on the circle to show the changes in the triangle.
Chord and its related theorems
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==Concept #1 CHORD==
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===Learning objectives===
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The students should be able to:<br>
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#Recall the meaning of circle and chord.<br>
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#State Properties of chord.<br>
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# By studying the theorems related to chords, the students should know that a chord in a circle is an important concept .
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# They should be able to relate chord properties to find unknown measures in a circle.
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# They should be able to apply chord properties for proof of further theorems in circles.
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===Notes for teachers===
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What is the condition with respect to sides for formation of a triangle. Sum of two sides is larger than the third side.
A chord is a straight line joining 2 points on the circumference of a circle. Chords within a circle can be related many ways. The theorems that involve chords of a circle are :
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Perpendicular bisector of a chord passes through the center of a circle.
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Congruent chords are equidistant from the center of a circle.
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If two chords in a circle are congruent, then their intercepted arcs are congruent.
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If two chords in a circle are congruent, then they determine two central angles that are congruent.  
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===Activity No 1 Theorem 1: Perpendicular bisector of a chord passes through the center of a circle. ===
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Compare the chord length with sum of two radii. When is the triangle reduced to a line segment.
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''[http://www.karnatakaeducation.org.in/?q=node/305 Click to Comment]''</div>
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*Estimated Time <br>
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20 minutes
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*Materials/ Resources needed:
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Laptop, Geogebra file, projector and a pointer.
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*Prerequisites/Instructions, if any
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# The students should know the basic concepts of a circle and its related terms.
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# They should have prior knowledge of chord and construction of perpendicular bisector to the chord.
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*Multimedia resources: Laptop
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*Website interactives/ links/ / Geogebra Applets
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What can you conclude about the chord? When is it the largest?
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*Process:
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[[Category:Circles]]
# Show the children the geogebra file.
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# Let them identify the chord. Ask them to define a chord.
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# perpendicular bisector.
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# Show them the 2nd chord.
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# Let students observe if everytime the perpendicular bisector of the chord passes through the centre of the circle.
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*Developmental Questions:
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# What is a chord ?
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# At how many points on the circumference does the chord touch a circle .
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# What is a bisector ?
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# What is a perpendicular bisector ?
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# In each case the perpendicular bisector passes through which point ?
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# Can anyone explain why does the perpendicular bisector always passes through the centre of the circle ?
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*Evaluation
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# What is the angle formed at the point of intersection of chord and radius ?
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# Are the students able to understand what a perpendicular bisector is ?
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# Are the students realising that perpendicular bisector drawn for any length of chords for any circle always passes through the center of the circle .
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*Question Corner:
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# What do you infer ?
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# How can you reason that the perpendicular bisector for any length of chord always passes through the centre of the circle.
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===Activity No # ===
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''[http://www.karnatakaeducation.org.in/?q=node/305 Click to Comment]''</div>
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*Estimated Time
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*Prerequisites/Instructions, if any
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*Process/ Developmental Questions
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*Evaluation
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*Question Corner
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==Concept #2.SECANT==
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===Learning objectives===
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===Notes for teachers===
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===Activity No # ===
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''[http://www.karnatakaeducation.org.in/?q=node/305 Click to Comment]''</div>
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*Estimated Time
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*Materials/ Resources needed
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''[http://www.karnatakaeducation.org.in/?q=node/305 Click to Comment]''</div>
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*Estimated Time
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*Prerequisites/Instructions, if any
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==Concept #3.TANGENT==
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===Learning objectives===
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===Notes for teachers===
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===Activity No # ===
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''[http://www.karnatakaeducation.org.in/?q=node/305 Click to Comment]''</div>
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*Estimated Time
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*Materials/ Resources needed
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*Prerequisites/Instructions, if any
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''[http://www.karnatakaeducation.org.in/?q=node/305 Click to Comment]''</div>
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*Estimated Time
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*Materials/ Resources needed
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*Prerequisites/Instructions, if any
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*Multimedia resources
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*Website interactives/ links/ / Geogebra Applets
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*Question Corner
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= Hints for difficult problems =
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= Project Ideas =
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= Math Fun =
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'''Usage'''
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