Testwiki:Reference desk/Archives/Mathematics/2008 August 24

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August 24

Math question

There's a quarter-circle ABC with centre O and radius unit 1. There is a point D which is the midpoint of OC and DB is parallel to OA. Ive tried to draw it roughly using characters cos i wasnt bothered to draw and upload a proper picture but it should give you a good idea of it.

 A |\\\
   |    \\  B
   |      / \\
   |    /     |
   |   /      | \\
   |  /       |    \\
   | /        |      \\
   |____________________
   O          D       C

I have been asked to "BY considering separately the triangle OBD and the sector OAB, show that the area of the shaded region OABD is 1/24(2π + 3 sqrt(3) )" I get sqrt(3)/8 for OBD and 1/12π for OAB. And cant get to the required answer. What am I doing wrong? By the way, this is not homework, Im just doing questions as part of my revision for my resits. --212.120.246.239 (talk) 17:19, 24 August 2008 (UTC)

Your answer is equal to the given answer. What's the problem? Algebraist 17:25, 24 August 2008 (UTC)

OK, let's try it:

$\frac{1}{24}(2\pi +3\sqrt{3})=(\frac{1}{24}\cdot 2\pi )+(\frac{1}{24}\cdot 3\sqrt{3})=\frac{2\pi }{2\cdot 12}+\frac{3\sqrt{3}}{3\cdot 8}$

In the first fraction the "2"s cancel and in the second fraction the "3"s cancel. You get

$\frac{\pi }{12}+\frac{\sqrt{3}}{8},$

the same thing you say you got. Michael Hardy (talk) 17:55, 24 August 2008 (UTC)

mathemetician

The name of the Greek mathemetician please —Preceding unsigned comment added by 84.45.143.243 (talk) 22:22, 24 August 2008 (UTC)

There have been a number of Greek mathematicians, including these guys and these guys. Algebraist 22:27, 24 August 2008 (UTC)

Perhaps after browsing Algebraist's suggestions, this or this or even this may be of interest. --hydnjo talk 23:30, 24 August 2008 (UTC)