My Math Forum  

Go Back   My Math Forum > High School Math Forum > Geometry

Geometry Geometry Math Forum


Thanks Tree1Thanks
Reply
 
LinkBack Thread Tools Display Modes
November 24th, 2017, 09:37 PM   #11
Global Moderator
 
Joined: Dec 2006

Posts: 18,247
Thanks: 1439

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.
skipjack is offline  
 
November 25th, 2017, 02:17 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(180-30) and simplify it then);
I tried his method, but it seems impossible/very ^10 hard.

Last edited by skipjack; November 25th, 2017 at 05:51 AM.
Ariel4 is offline  
November 25th, 2017, 05:47 AM   #13
Math Team
 
Joined: Oct 2011
From: Ottawa Ontario, Canada

Posts: 11,072
Thanks: 722

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 5-12-13,
stuck together along side 12.

Good luck.
Denis is offline  
November 25th, 2017, 05:58 AM   #14
Global Moderator
 
Joined: Dec 2006

Posts: 18,247
Thanks: 1439

Quote:
Originally Posted by Ariel4 View Post
As he said, it can be solved without calculator, . . .
If that's the case, the teacher inadvertently annotated the diagram incorrectly. For example, he might have interchanged the component angles at A and also interchanged the component angles at B.
skipjack is offline  
November 25th, 2017, 08:04 AM   #15
Newbie
 
Joined: Nov 2017
From: Serbia

Posts: 6
Thanks: 0

Quote:
Originally Posted by skipjack View Post
If that's the case, the teacher inadvertently annotated the diagram incorrectly. For example, he might have interchanged the component angles at A and also interchanged the component angles at B.
Nope, the diagram is correctly written. Someone in my class mention that he maybe gave as wrong angles but when he checked it again it was all good.

Quote:
Originally Posted by Denis View Post
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 5-12-13,
stuck together along side 12.

Good luck.
I will try to research more about inscribed angles but think I have a good understanding of geometry and trig in general, at least for my age and in my class.I hope I'll find a solution, this problem is bothering me for a long time now.
Ariel4 is offline  
November 25th, 2017, 01:50 PM   #16
Global Moderator
 
Joined: Dec 2006

Posts: 18,247
Thanks: 1439

Did your teacher confirm that the answers obtained to several decimal places are correct?
skipjack is offline  
November 26th, 2017, 01:59 AM   #17
Newbie
 
Joined: Nov 2017
From: Serbia

Posts: 6
Thanks: 0

Quote:
Originally Posted by skipjack View Post
Did your teacher confirm that the answers obtained to several decimal places are correct?
When I told him the answers everything he said is, quote "That's not correct, I don't want you to solve this problem with approximate angles, and it can be solved with inscribed(peripheral) angles and adding few lines inside of triangle"
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...
Ariel4 is offline  
November 26th, 2017, 06:17 AM   #18
Math Team
 
Joined: Oct 2011
From: Ottawa Ontario, Canada

Posts: 11,072
Thanks: 722

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
Denis is offline  
November 27th, 2017, 11:58 AM   #19
Senior Member
 
Joined: Dec 2015
From: holland

Posts: 157
Thanks: 37

Math Focus: tetration
Angle OED = -5
Angle ODE = 55
manus is offline  
November 27th, 2017, 12:04 PM   #20
Senior Member
 
Joined: Dec 2015
From: holland

Posts: 157
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
manus is offline  
Reply

  My Math Forum > High School Math Forum > Geometry

Tags
solvegeometry or triangle



Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Geometry (triangle) Prince Elementary Math 2 May 4th, 2014 03:41 AM
Geometry-Triangle Aman Verma Geometry 2 December 15th, 2013 01:40 AM
triangle geometry biosavart Geometry 6 December 8th, 2010 08:37 PM
Geometry - triangle macciej Geometry 3 October 26th, 2009 09:31 PM





Copyright © 2017 My Math Forum. All rights reserved.