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September 13th, 2013, 07:02 AM   #1
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help (the area of a sector)

I'm using Basic Mathematics by Serge Lang & I'm currently on the geometry section of the book. He explained angles & their measurements in degrees, then on how to get the area of the sector formed by two rays.

area of S = x/360 multiplied by the area of the disc

One of the exercises goes like this. It gives you a 60 degree angle and the area of the disc, which is 60 in^2

So I look for the ratio between the angle and the full circle

60/360 = 1/6

then I multiply that by the area of the disc 60 in^2

= 10 in^2

but the book says the answer is 1

Am I doing anything wrong or is it the book?
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September 13th, 2013, 07:42 AM   #2
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Re: help (the area of a sector)

The book has made an error.
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September 13th, 2013, 12:33 PM   #3
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It's likely that the book should have given 6 in as the area of the disc instead of 60 in. A reviewer on Amazon specifically notes that there are many discrepancies between the questions and the answers in this book. However, most other aspects of the book are favourably reviewed.
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