GeoGebra-5.04/C2/Properties-of-Quadrilaterals/English-timed

Time	Narration
00:01	Welcome to this tutorial on Properties of Quadrilaterals in GeoGebra.
00:07	In this tutorial we will learn, To construct quadrilaterals and understand the properties of quadrilaterals using GeoGebra.
00:19	Here I am using: Ubuntu Linux OS, version 14.04 GeoGebra version 5.0.438.0-d
00:31	To follow this tutorial, learner should be familiar with GeoGebra interface.
00:38	If not for relevant GeoGebra tutorials, please visit our website.
00:44	Let us begin our demonstration.
00:47	I have already opened the GeoGebra interface.
00:51	For this tutorial, I will first uncheck the Axes.
00:55	To do that, right-click on Graphics view. The Graphics menu opens.
01:01	Click on the Axes check-box.
01:04	I will increase the font size for better view.
01:08	Go to Options menu, navigate to Font Size.
01:13	From the sub-menu, select 18 pt radio button.
01:17	Now let us construct a parallelogram.
01:20	Click on the Segment with Given Length tool.
01:24	Click on the Graphics view.
01:27	The Segment with Given Length text box opens.
01:31	In the Length field, type 5 and click on OK button.
01:37	Segment AB with length 5 cm and labelled as f, is drawn.
01:44	Let us delete the point that was drawn mistakenly.
01:48	This point may not be required for the actual drawing.
01:52	Right-click on the point. From the sub-menu, select the Delete option.
01:59	Next click on the Parallel Line tool.
02:02	Click below line AB to draw point C then click on line AB.
02:09	A parallel line to segment AB passing through C, is drawn.
02:14	Using Segment tool, join the points A and C.
02:21	Click again on Parallel Line tool, click on segment AC and then click on point B.
02:31	Two parallel lines g and i intersect at a point.
02:36	Click on Intersect tool and click on the point of intersection as D.
02:43	Now using the Segment tool, join the points, C, D and D, B.
02:53	Parallelogram ABDC is now complete.
02:57	We will hide the lines g and i, so that we can see the parallelogram clearly.
03:04	Right-click on line g, from the submenu click on Show Object check-box. Similarly I will hide the line i.
03:15	Now we will explore the properties of parallelogram ABDC.
03:20	From the Algebra view, we can find that, segments f and j are equal and segments h and k are equal.
03:31	Observe that, the opposite sides are parallel and equal.
03:36	Let us now measure the angles of the parallelogram.
03:40	Click on Angle tool. Click on the points D C A
03:50	C A B
03:55	A B D
04:01	B D C.
04:07	Observe that the opposite angles are equal.
04:11	Now we will convert the parallelogram ABDC to a rectangle.
04:16	Click on Move tool. Click and drag point C until you see 90 degrees angle.
04:25	Drag the labels to see them clearly.
04:30	Observe that all the angles changed to 90 degrees.
04:34	Now let us learn to construct a kite.
04:37	For this I will open a new GeoGebra window.
04:41	Click on File and select New Window.
04:46	To contruct a kite, we will draw two circles that intersect at two points.
04:52	Click on Circle with Centre through point tool.
04:55	Then click on Graphics view.
04:58	Point A is drawn, this is the centre of the circle.
05:03	Click again at some distance from point A.
05:07	Point B appears. This completes the circle c.
05:13	Similarly, we will draw another circle with centre C and passing through D.
05:21	Notice that the two circles c and d intersect at two points.
05:26	Click on Intersect tool and click on the circles c and d.
05:33	E and F are the intersection points of the circles.
05:37	Now let us draw the required quadrilateral using these circles.
05:42	Click on Polygon tool.
05:44	Click on the points A, E, C, F and A again to complete the quadrilateral.
05:57	Notice in the Algebra View that two pairs of adjacent sides are equal. The drawn quadrilateral is a kite.
06:06	Pause the tutorial and do this assignment.
06:10	Measure the angles of the kite and check what happens.
06:14	Draw diagonals and locate the intersection point of the diagonals.
06:19	Measure the angle at the intersection of the diagonals.
06:23	Check if diagonals bisect each other.
06:27	Your completed assignment should look like this.
06:32	To delete all the objects, press Ctrl + A and then press Delete key on the Key board.
06:40	Now let us construct a rhombus.
06:43	Click on Segment with Given Length tool. Click on the Graphics view.
06:49	Segment with Given Length text box opens.
06:53	In the Length field, type 4 and click on OK button. A segment with 4 units is drawn.
07:03	Let us construct a circle with center A and passing through B.
07:08	Click on Circle with Centre through Point tool.
07:11	Click on points A and B to complete the circle.
07:17	Using Point tool, mark a point C on the circumference of the circle.
07:23	Click on Segment tool and then click on points A and C.
07:29	This will join the points A and C.
07:32	Click on the Parallel line tool and click on the line AB and then on point C.
07:41	We see a line parallel to AB passing through C.
07:46	Similarly, draw a parallel line to segment AC passing through B.
07:53	Notice that the lines i and h intersect at a point.
07:58	Using Intersect tool, we will mark the point of intersection as D.
08:05	Using the Segment tool, join the points A, D and B, C.
08:13	A quadrilateral ABDC with diagonals AD and BC is drawn.
08:19	The diagonals intersect at a point. Using Intersect tool, mark the point of intersection as E.
08:30	Pause the tutorial and do this assignment.
08:34	Check if the diagonals of the quadrilateral ABDC bisect each other.
08:40	Also check if the diagonals are perpendicular bisectors.
08:45	Your completed assignment should look like this.
08:49	Now let us construct a cyclic quadrilateral.
08:53	For this, let us open Graphics 2 view.
08:57	Go to View menu and select Graphics 2 check box.
09:03	Graphics 2 view window opens, next to existing Graphics view.
09:08	Drag the border of the existing Graphics view, to see Graphics 2 view.
09:13	Now select Regular Polygon tool. Click twice on Graphics 2 view.
09:20	The Regular Polygon text box opens with default value 4.
09:25	Click on the OK button.
09:28	A square FGHI is drawn in Graphics 2 view.
09:33	Let's construct perpendicular bisectors to segments FG and GH.
09:39	Select the Perpendicular Bisector tool from the tool bar.
09:43	Click on the points F, Gand G, H.
09:50	Observe that the perpendicular bisectors intersect at a point.
09:55	Using Intersect tool we will mark this point as J.
10:01	Now, Let's construct a circle with centre as J and passing through F.
10:07	Click on the Circle with center through Point tool, click on point J. Then click on point F.
10:16	A cyclic quadrilateral FGHI is drawn.
10:21	Now we will display its area.
10:24	From the Angle tool drop down, click on the Area tool.
10:28	Then click on the quadrilateral FGHI to display its area.
10:35	As an assignment, Draw a trapezium
10:40	Measure its perimeter and area.
10:44	Your completed assignment should look like this.
10:49	Let us summarise what we have learnt.
10:52	In this tutorial we have learnt, To construct quadrilaterals and understand the properties of quadrilaterals using GeoGebra.
11:03	The video at the following link summarises the Spoken Tutorial project. Please download and watch it.
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11:36	This is Madhuri Ganapathi from, IIT Bombay signing off. Thank you for watching.

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