Geometer's sketchpad is nice too, for drawing and getting results quickly.

Richard Stallman wrote:

]]>Proprietary software is itself an injustice.

You can also use Geogebra which is a free download.

Also, it is mostly free software. Parts of GPL and CC BY-SA.

The freedom of commercially using the modified code is prohibited, though.

]]>Where did you draw this also?

You should be able to see a diagram in post 5. If you meant 'what software am I using?' it's called Geometers Sketchpad. You can also use Geogebra which is a free download.

The notation is done using Latex. If you click on some, you'll get a window showing the actual code. You enclose it in square brackets math /math to switch in the Latex handling program.

There's a tutorial at

http://www.mathisfunforum.com/viewtopic.php?id=4397

and you and set up code using the editor at

http://latex.codecogs.com/eqneditor/editor.php

Bob

]]>Area of the biggest semi circle minus the area of the two smaller semicircles. Once you cancell down you get 1/4 pi AD times DB

Then:

You have now have a right angled triangle by the inscribed angle rule. You can now apply pythagorus theorem.

AB^2 = AC^2 + CB^2 Now AC is the hypotenuse of triangle ACD

CB is the hypotenuse of triangle CDB

So AB^2 = AD^2 + CD^2 + CD^2 + DB^2

AB^2= AD^2 + 2CD^2 + DB^2

bla bla bla

2AD x DB = 2CD^2

AD x DB = CD^2

so replace AD x DB by CD^2

]]>See diagram below.

Your diagram is a special case where ADB is a diameter. => chord CE is bisected by ADB so CE = DE.

b

How do you write out the notation like this? I think I have another solution that works.

]]>We have used this property in lower grades to mark irrational numbers like sqrt(2) on the real number line.

Long, long ago, when I was doing O level Technical drawing, we used it to construct (compass, set square and straight edge only) a square equal in area to a given rectangle.

We also learnt how to use construction techniques to do:

n sided polygon ---> equal area n-1 sided polygon

triangle ---> equal area rectangle

Thus you can convert any polygon to an equal area square.

But not a circle

Bob

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