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April 2nd, 2011, 12:48 PM  #1 
Newbie Joined: Apr 2011 Posts: 2 Thanks: 0  determine angle B 
April 2nd, 2011, 10:30 PM  #2 
Senior Member Joined: Apr 2007 Posts: 2,140 Thanks: 0 
?BAC + ?ABC : ?ACB = 320 : 40 = 8 : 1 180° = 8x + x = 9x x = 20° ? ?BAC + ?ABC = 160° ? ?ACB = 20° 
April 3rd, 2011, 08:58 PM  #3 
Newbie Joined: Apr 2011 Posts: 2 Thanks: 0  Re: determine angle B
thank you for your help, although i cant fully understand the solution, i am not very good at math could you give me a brief explanation please? regards 
April 4th, 2011, 02:38 AM  #4 
Senior Member Joined: Apr 2007 Posts: 2,140 Thanks: 0 
We know that arc c is 40°, hence arc a + arc b is 320° in order to make 360° rotation possible. ?ACB depends on arc c and ?BAC + ?ABC depends on arc a + arc b. ?ACB + ?BAC + ?ABC = 180° and 8?ACB = ?BAC + ?ABC, hence ?ACB + 8?ACB = 9?ACB = 180°. ? ?ACB = 20°, ?BAC + ?ABC = 160° 
April 4th, 2011, 04:40 AM  #5 
Global Moderator Joined: Dec 2006 Posts: 18,034 Thanks: 1393 
The question asks for angle B, not C. You would need additional information to determine B.


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