Chandrika: Created page with '[http://spoken-tutorial.org/wiki/index.php/File:Angles_Triangles_Basics.zip Click here for Slides]

2012-11-27T08:35:28Z
Created page with '[http://spoken-tutorial.org/wiki/index.php/File:Angles_Triangles_Basics.zip Click here for Slides] <DIV ALIGN=RIGHT> <TABLE WIDTH=642 BORDER=1 BORDERCOLOR="#000000" CELLPADDIN…'
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[http://spoken-tutorial.org/wiki/index.php/File:Angles_Triangles_Basics.zip Click here for Slides]

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Visual
Cue
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Narration
with timings
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Show
slide number 1
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Hello
Everybody. Welcome to the Geogebra tutorial Angles and Triangles
Basics. 

 

If
this is the first time you are using Geogebra, please see the
“Introduction to Geogebra” Tutorial on the spoken tutorial
website.
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Switch
to slide number 2
(Lesson
Objective ) 

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To
get started with Geogebra, I am using the Linux operating system
Ubuntu Version 10.04 LTS and Geogebra Version 3.2.40.0

 


The
objective of this tutorial is to verify that the sum of the
interior angles of a triangle is always 180 degrees using
Geogebra
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Switch
to slide number 3 

(Lesson
Outline)
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In
this tutorial, we will learn to use the Polygon, Angle
and Insert Text tool.
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Switch
to Geogebra Window
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Now
First select the polygon tool. To draw a polygon, in this case a
triangle, select the three vertices by clicking on the drawing
pad. Then click the first vertex.

 


To
measure the interior angles of the triangles, select the angle
tool. You can measure the angle in two ways. Click clock wise the
three vertices , A, B then t C, this measures the angle ABC
named Alpha.

 


The
second way is to select the line segments that form the angle.
Select segment a and Segment b, this time
anti-clockwise to get angle BCA named beta.

 


 


Similarly
CAB, will measure the angle gamma.

 


Note
all angles are named according to standard mathematical
convention as Greek alphabets 


 


Also
if you select the vertices anti clockwise like this , C B A then
the exterior angle is measured.

 


To
add text to your drawing pad, use the insert Text Tool. Then
click anywhere on the drawing pad, a text window appears 


 


Now
to display Angle ABC, type within double quotes Angle ABC =
, close double quotes, add the + sign and then click on alpha.
Say OK. So n I get the value of Angle ABC

 


 


Similarly
to do arithmetic, to display the sum of the interior angles of
this triangle, click on the insert text tool, click here on the
drawing pad type in within double quotes Sum of interior
angles of triangle ABC = , close double Quotes plus and open
curly brackets select alpha + beta + gamma close curly brackets.
Say OK. Now you see the sum displayed.

 


Next
Select the move tool and move the free objects in this case the
vertices A B or C and you will notice that the sum of the
interior angles of triangle ABC is always 180 degrees.

 


My
favourite part of this lesson is to show how when all the three
vertices of the triangle are on a straight line - reduces two of
the interior angles to zero and the third becomes 180 degrees
like this a Straight Angle. 

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Switch
to Slide 3
(Drawing
Pad Properties)
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Next
we will learn two more things, the drawing pad properties and how
to delete an object in Geogebra
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Geogebra
Window – Drawing Pad Properties
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First
the drawing pad properties. Right click anywhere on the drawing
pad and then click on drawing pad

 


The
drawing pad properties window opens. You can change the
background colour of the drawing pad here.

 


Change
properties of the axes here, both the X Axis and the Y axis here
and you can change the properties of the grid here.

 


Some
properties to note are the unit you can add for the axis and the
labels you can add for the axis and the x axis to Y axis ratio. 


 


When
we are doing simple geometry we usually would like to keep it a
1:1 ratio. 


 


When
you close all changes you have made will be saved

 

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The
Delete Option in Geogebra
 

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Now
To delete an object on the drawing pad, move the mouse over the
object, I will move the mouse over the external angle , right
click you will notice that the object name appears here and then
say delete, then the object is deleted. 


 


Another
way of deleting an object is to select the object on the algebra
view, right click on it and say delete an object on the algebra
view 


 


Notice
when I delete the angle gamma this text also disappears because
it is dependent on the angle Gamma

 


If
I want to undo what I've deleted just edit click undo or
press CRTL Z 


 


To
delete multiple objects in Geogebra the easiest way to do it is
to left click anywhere on the drawing pad, drag the mouse over
all the objects you want to delete, undo the click, all the items
are selected and then hit delete on your keyboard. 


 


Again
lets undo this by clicking undo

 

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Switch
to Slide 4
(Writing
the Text 1 )
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Now
I would like to explain the syntax of the text once again.

 


Text
that needs to appear as-is must be within double quotes ””.As
seen in the example 


 


For
values of Geogebra variables use the variable name as seen in the
algebra view without quotes. 


 

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Switch
to Slide 5
(Writing
the Text 2 )
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To
do arithmetic with the values use the variables within curly
brackets (). 


 


Finally
to concatenate or connect text use the + sign. 


 

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Switch
to Slide 6 

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Next
we will just look at some ways of matching the colours of the
angles and the text

 


 

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Geogebra
Window – Object Properties
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Now if
I want to change the text colour I will right click and select
object properties, go to colour and change the colour and say
close
 

Now I
can go to the angle here, right click , select object properties
I can choose the resent window here and click on this colour for
an exact match
 

Similarly
if I want to zoom in and zoom out I use the zoom in here to zoom
in and the zoom out option, click on the drawing pad to zoom out.
 

To
change the angle unit I can go to options, angle unit and change
from degrees to radians.
 

 

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Switch
to Slide 6
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So
just to recap I know how to change the angle measure from radians
to degrees , I can zoom in and zoom out
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Switch
to Slide 7
(Assignment)
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Now
to the ASSIGNMENT. 

 

Draw
to verify - Exterior Angle of a Triangle is equal to the sum of
the opposite Interior Angles 

 

Do
the following steps Draw a triangle using the polygon tool 

 

Extend
any one of the sides using the line through two points tool 

 

Use
the angle tool to measure the exterior angle and the opposite
interior angles 

 

Use
the Insert Text tool to display the results Verify this by using
the Move tool and moving the free objects 

 

Verify
the theorem by using the move tool and moving the free objects. 

 

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Switch
to Geogebra File Triangle Exterior Angle.ggb 

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I
will show you what I have done. You just need to move the move
tool and move the free objects. 

 

You
will notice that the exterior angle is always equal to the sum of
the opposite interior angles.
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Switch
to Slide 8
(Acknowledgement)
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I
would like to acknowledge the spoken tutorial project which is
part of the talk to a teacher project. 

 

It
is supported by the National Mission on Education through ICT,
MHRD government of India.
 

You
can see more information about this at this website. 

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Switch
to Slide 9
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Thank
you this is Bindu signing off. Enjoy exploring Geogebra.
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← Older revision		Revision as of 09:40, 18 December 2013
Line 1:		Line 1:
		+	Title of the tutorial: Angles-and-Triangles-Basics
		+
		+	Author: Bindu Thirumalai
		+
		+	Key words: Polygon, Angle and Insert Text tools, drawing pad properties, background colour, concatenate, delete, Video tutorial.
		+
	[http://spoken-tutorial.org/wiki/index.php/File:Angles_Triangles_Basics.zip Click here for Slides]		[http://spoken-tutorial.org/wiki/index.php/File:Angles_Triangles_Basics.zip Click here for Slides]

Geogebra/C2/Angles-and-Triangles-Basics/English - Revision history

Madhurig at 09:40, 18 December 2013

Pravin1389 at 14:32, 28 November 2012

Pravin1389 at 14:30, 28 November 2012

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