November 24th, 2017, 08:37 PM  #11 
Global Moderator Joined: Dec 2006 Posts: 19,515 Thanks: 1745 
That's why I provided a correctly scaled diagram. It's accurate except for a very slight increase in the slope of the line ED.

November 25th, 2017, 01:17 AM  #12 
Newbie Joined: Nov 2017 From: Serbia Posts: 6 Thanks: 0 
Picture is out of scale that's for sure. Denis thank you for this solution, but when I told teacher about this solution he said that this is not the way I was supposed to solve this. As he said, it can be solved without calculator, using peripheral angles and representing angles with another one (don't know right term in English, but, for example, cos150 => cos(18030) and simplify it then); I tried his method, but it seems impossible/very ^10 hard. Last edited by skipjack; November 25th, 2017 at 04:51 AM. 
November 25th, 2017, 04:47 AM  #13 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 13,115 Thanks: 913 
Nice description of peripheral angles here: https://en.wikipedia.org/wiki/Inscribed_angle But gives me a headache! Perhaps a good way for you to "get it" is use a triangle of known size and work with it; like a triangle made up of 2 right triangles: suggest 2 right triangles each 51213, stuck together along side 12. Good luck. 
November 25th, 2017, 04:58 AM  #14 
Global Moderator Joined: Dec 2006 Posts: 19,515 Thanks: 1745  
November 25th, 2017, 07:04 AM  #15  
Newbie Joined: Nov 2017 From: Serbia Posts: 6 Thanks: 0  Quote:
Quote:
 
November 25th, 2017, 12:50 PM  #16 
Global Moderator Joined: Dec 2006 Posts: 19,515 Thanks: 1745 
Did your teacher confirm that the answers obtained to several decimal places are correct?

November 26th, 2017, 12:59 AM  #17  
Newbie Joined: Nov 2017 From: Serbia Posts: 6 Thanks: 0  Quote:
Then when I told him that answer we get is not nice number as I checked on GeoGebra he just smiled and said that I shouldn't worry and that the solution we get on end is nice number.I'm considering now to message him and ask him to check again the solution for this problem and way we should solve it...  
November 26th, 2017, 05:17 AM  #18 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 13,115 Thanks: 913 
This seems to be the original problem: Angular Angst Your diagram is not quite the same: the 50:30 (angleCAB) should be 30:50 the 60:20 (angleCBA) should be 20:60 
November 27th, 2017, 10:58 AM  #19 
Senior Member Joined: Dec 2015 From: holland Posts: 163 Thanks: 37 Math Focus: tetration 
Angle OED = 5 Angle ODE = 55 
November 27th, 2017, 11:04 AM  #20 
Senior Member Joined: Dec 2015 From: holland Posts: 163 Thanks: 37 Math Focus: tetration 
Angle OED + Angle ODE = 50 Angle CED + Angle CDE = 160 Angle OED + Angle CED = 100 Angle ODE + Angle CDE = 110 

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