Geogebra/C3/Relationship-between-Geometric-Figures/English-timed

Title of script: Relationship between different Geometric Figures

Author: Madhuri Ganapathi

Keywords: video tutorial

Time	Narration
00:00	Hello.
00:01	And welcome to the spoken tutorial on Relationship between different Geometric Figures in Geogebra
00:07	We assume that you have the basic working knowledge of Geogebra.
00:11	If not, please go through the Introduction to Geogebra tutorial before proceeding further.
00:18	Please note that the intention to teach this tutorial is not to replace the actual compass box.
00:24	Construction in GeoGebra is done with the view to understand the properties.
00:29	In this tutorial we will learn to construct
00:32	Cyclic quadrilateral and In-circle
00:35	To record this tutorial I am using Linux operating system
00:39	Ubuntu Version 10.04 LTS
00:43	And Geogebra Version 3.2.40.0
00:48	We will use the following Geogebra tools for the construction compass segment between two points circle with center through point polygon perpendicular bisector angle bisector and angle
01:02	Let us switch on to the Geogebra window.
01:05	To do this let us click on applications, Education and Geogebra.
01:13	Let me resize this window.
01:18	Click on the options menu click on font size and then on 18 point to make the figure clear.
01:25	Let us construct a cyclic quadrilateral.
01:27	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.
01:38	We see that a dialog box open with a default value 4.
01:42	click OK.
01:43	A square ABCD is drawn.
01:46	Let's tilt the square Using the Move tool which is at the left corner.
01:51	Select the Move tool from the tool bar, click on the Move tool
01:56	Place, the mouse pointer on A or on B. I will choose B
02:01	Place the mouse pointer on B and drag it with the mouse. We see that the square is in the tilted position now.
02:10	Let's construct a perpendicular bisector to the segment AB.
02:15	To do this Let's Select Perpendicular bisector tool from the tool bar.
02:20	Click on the Perpendicular bisector tool.
02:22	click on the point A
02:24	and then on pointB
02:26	We see that a Perpendicular bisector is drawn.
02:30	Let's construct a second perpendicular bisector to segment BC to do this
02:36	Select perpendicular bisector tool from the tool bar, click on the “perpendicular bisector” tool.
02:42	click on the point B
02:44	and then on point C
02:46	We see that the perpendicular bisectors intersect at a point .
02:50	Let us mark this point as E
02:54	Let's now construct a circle with centre as E and which passes through C.
03:01	Let's select the circle with centre through point tool from tool bar click on the circle with centre through point tool.
03:09	Click on point E as centre and which passes through C. Click on the point E and then on point C.
03:18	We see that the circle will passes through all the vertices of the quadrilateral.A Cyclic Quadrilateral is drawn.
03:29	Do you know , that the cyclic quadrilateral has maximum area among all the quadrilaterals of the same sequence of side lengths.
03:37	Let's use the Move tool, to animate the figure.
03:42	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
03:52	Place the mouse pointer on A and drag it with the mouse to animate.
03:58	To verify that the construction is correct.
04:01	Let's now save the file.
04:04	Click on File Save As.
04:07	I will type the file name as cyclic_quadrilateral
04:21	and click on save
04:23	Let us now open a new geogebra window to construct an incircle.
04:28	To do this Let's select on File and New.
04:35	Let's now construct a triangle to do this , Let's select the Polygon tool from the tool bar, Click on the Polygon tool.
04:44	click on the points A,B,C and A once again to complete the triangle figure.
04:52	Let's measure the angles for this triangle,
04:55	To do this Let's select the Angle tool from the tool bar, click on the Angle tool.
05:00	Click on the points B,A,C , C,B,A and A,C,B.
05:15	We see that the angles are measured.
05:18	Lets now construct angle bisectors to these angles.
05:21	Select the Angle bisector tool from the tool bar,
05:25	click on the Angle bisector tool.Click on the points B,A,C .
05:32	Let's select the Angle bisector tool again from the tool bar to construct second angle bisector.
05:39	click on the Angle bisector tool and the tool bar, click on the points A,B,C.
05:48	We see that the two angle bisectors intersect at point .
05:52	Let's mark this point as D.
05:55	Let's now construct a perpendicular line which passes through point D and segment AB.
06:02	Select perpendicular line tool from tool bar,click on the perpendicular line tool, click on the point D and then on segment AB.
06:12	We see that the perpendicular line intersects segment AB at a point.
06:17	Let's mark this point as E.
06:20	Let's now construct a circle with centre as D and which passes through E.
06:27	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.
06:37	Click on the point D and then on point E and D once again to complete the figure.
06:46	We see that the circle touches all the sides of the triangle.
06:50	An in-circle is drawn.
06:53	With this we come to an end of this tutorial.
06:57	To Summarize
07:02	In this tutorial we have learnt to construct
07:05	cyclic quadrilateral and
07:07	In-circle using the Geogebra tools.
07:10	As an assignment i would like you to draw a triangle ABC
07:15	Mark a point D on BC, join AD
07:19	Draw in-circles form triangles ABC, ABD and CBD of radii r, r1 and r2 .
07:28	BE is the height h
07:30	Move the vertices of the Triangle ABC
07:33	To verify the relation.
07:35	(1 -2r1/h)*(1 - 2r2/h) = (1 -2r/h)
07:43	The output of the assignment should look like this.
07:52	Watch the video available at this URL.
07:55	It summarises the Spoken Tutorial project.
07:57	If you do not have good bandwidth, you can download and watch it
08:02	The Spoken Tutorial Project Team :Conducts workshops using spoken tutorials.
08:06	Gives certificates to those who pass an online test
08:09	For more details, contact us contact@spoken-tutorial.org
08:16	Spoken Tutorial Project is a part of Talk to a Teacher project
08:19	It is supported by the National Mission on Education through ICT, MHRD, Government of India.
08:25	More information on this Mission is available at this link.
08:29	This is Madhuri Ganapathi from IIT Bombay signing off Thanks for joining.

Contributors and Content Editors

Madhurig, Minal, Nancyvarkey, PoojaMoolya, Pratik kamble, Sandhya.np14