Difference between revisions of "Geogebra/C3/Relationship-between-Geometric-Figures/English-timed"

!Narration

||Hello.  

 

||And welcome to the spoken tutorial on Relationship between different Geometric Figures in Geogebra

||We assume that you have the basic working knowledge of Geogebra.   

||If not, please go through the “Introduction to Geogebra” tutorial before proceeding further.

||Construction in GeoGebra is done with the view to understand the properties.

||In this tutorial we will learn  to construct

||Cyclic quadrilateral and In-circle

||To record this tutorial I am using

Linux operating system   

||Ubuntu Version  10.04 LTS  

||And Geogebra Version 3.2.40.0  

||We will use the following Geogebra tools for  the construction

 

* segment between two points

 

* circle with center through point

 

 

 

* angle bisector and

 

||Let us switch on to the Geogebra window.

||To do this let us click on applications, Education and Geogebra.  

 

||Click on the options menu click on font size and then on 18 point to make the figure clear.

 

|| To do this let us select the "Regular Polygon" tool from the tool bar click on the "Regular Polygon" tool click on any two points on the drawing pad.

||We see that a dialog box open with a default value '4'.

||click OK.  

 

 

||A square  'ABCD' is drawn.  

 

||Let's tilt the square Using the “Move” tool which is at the left corner.

||Select the "Move" tool from the tool bar, click on the Move tool

||Place, the mouse pointer on  'A' or on 'B'. I will choose B  

||Place the mouse pointer on B and drag it with the mouse. We see that the square is in the tilted position now.

||Let's construct a perpendicular bisector to the segment 'AB'.  

||To do this Let's Select “Perpendicular bisector” tool from the tool bar.

||Click on the "Perpendicular bisector" tool.  

||click on the point 'A'  

||and then on  point'B'  

||We see that a "Perpendicular bisector" is drawn.

||Let's construct a second perpendicular bisector to segment 'BC' to do this   

||Select “perpendicular bisector” tool from the tool bar, click on the  “perpendicular bisector” tool.

||click on the point 'B'  

||and then  on point 'C'  

||We see that the perpendicular bisectors intersect at a point .

||Let us mark this point as 'E'

||Let's now construct a circle with centre as 'E' and which passes through C .

||Let's select the "circle with centre through point" tool from tool bar click on the "circle with centre through point" tool.

||Click on point 'E' as centre and which passes through 'C'. Click on the point 'E' and then on point 'C'.

||We see that the circle will passes through all the vertices of the quadrilateral.A Cyclic Quadrilateral is drawn.

||Do you know , that the cyclic quadrilateral has maximum area among all the quadrilaterals of the same sequence of side lengths.

||Let's use the "Move" tool, to animate the figure.

||To do this Let's select the "Move" tool from the tool bar, click on the "Move" tool place the mouse pointer on 'A' or 'B'. I will choose 'A'.

 

||Place the mouse pointer on 'A' and drag it with the mouse to animate.

||To verify that the construction is correct.

||Click on "File"  "Save As".   

||I will type the file name as "cyclic_quadrilateral"

||and click on save

||Let us now open a new geogebra window to construct an incircle.  

||To do this Let's select on File and New.

||Let's now construct a triangle to do this , Let's select the "Polygon" tool from the tool bar, Click on the "Polygon" tool.

||click on the points A,B,C and A once again to complete the triangle figure.   

||Let's measure the angles for this triangle,  

||To do this Let's select the "Angle" tool from the tool bar, click on the Angle tool.

 

||Click on the points 'B,A,C' , 'C,B,A' and 'A,C,B'.

||Select the "Angle bisector" tool from the tool bar,  

||click on the "Angle bisector" tool.Click on the points 'B,A,C' .

||Let's select the "Angle bisector" tool again from the tool bar to construct second angle bisector.

||click on the "Angle bisector" tool and the tool bar, click on the points A,B,C.

||We see that the two angle bisectors intersect at point .

||Let's mark this point as 'D'.

||Let's now construct a perpendicular line which passes through point D and segment AB.

||Select “perpendicular line” tool from tool bar,click on the “perpendicular line” tool, click on the point D and then on segment AB.

||We see that the perpendicular line intersects segment AB at a point.

||Let's mark this point as 'E'.

||Let's now construct a circle with centre as D and which passes through 'E'.

||Let's select the "compass" tool from tool bar , click on the "compass" tool,click on the point D as centre and DE as radius.

||Click on the point 'D' and then on point 'E' and 'D' once again to complete the figure.

||An in-circle is drawn.

||With this we come to an end of this tutorial.

||To Summarize  

||In this tutorial we have learnt to construct  

||In-circle using the Geogebra tools.

||As an assignment i would like you to draw a triangle ABC

||Mark a point D on BC, join AD  

||Draw in-circles form triangles ABC, ABD and CBD of radii r, r1 and r2 .  

||BE is the height h  

||Move the vertices of the Triangle ABC

||To verify the relation.

||It summarises the Spoken Tutorial project.

||If you do not have good bandwidth, you can download  

and watch it  

||Gives certificates to those who pass an online test  

||For more details, contact us contact@spoken-tutorial.org  

||Spoken Tutorial Project is a part of Talk to a Teacher project  

||More information on this Mission is available at this link.  

||This is Madhuri Ganapathi from IIT Bombay signing off

 

Thanks for joining.