Difference between revisions of "Geogebra/C3/Relationship-between-Geometric-Figures/English-timed"
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Revision as of 10:57, 23 February 2015
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 incircle. |
| 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:
|
| 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 opens 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 a 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
