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September 13th, 2013, 06:02 AM  #1 
Newbie Joined: Apr 2013 Posts: 8 Thanks: 0  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? 
September 13th, 2013, 06:42 AM  #2 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 520 Math Focus: Calculus/ODEs  Re: help (the area of a sector)
The book has made an error.

September 13th, 2013, 11:33 AM  #3 
Global Moderator Joined: Dec 2006 Posts: 20,469 Thanks: 2038 
It's likely that the book should have given 6 in² as the area of the disc instead of 60 in². 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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