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 22nd, 2017, 02:54 PM   #1
Newbie
 
Joined: Nov 2017
From: Serbia

Posts: 6
Thanks: 0

Is this possible to solve?Geometry/Triangle

So my teacher gave this math problem to us so we can solve it; he said that it is very hard even for him to do it.The person who solves it till tomorrow will get 2x A (double A's, double 5). I can't do it; I tried everything, but it just seems impossible. I'm 17 y.o., third grade in high school. I hope someone can help me with this.

-->We need to find those two angles that are marked on the picture; everything we know is marked and numbers on the picture are angles in degrees. Can you solve this and tell me how you get those answers? I need this ASAP. Thanks in advance!

Last edited by skipjack; November 22nd, 2017 at 06:12 PM.
Ariel4 is offline  
 
November 22nd, 2017, 06:08 PM   #2
Global Moderator
 
Joined: Dec 2006

Posts: 18,248
Thanks: 1439

Check your diagram with the teacher. If the diagram is correct, the problem is unfairly difficult. See this discussion.

HardTriangle.jpg

In the diagram above, the angles are 32° and 18°, but the discussion above indicates these values are only approximately correct.
skipjack is offline  
November 23rd, 2017, 02:10 AM   #3
Newbie
 
Joined: Nov 2017
From: Serbia

Posts: 6
Thanks: 0

Quote:
Originally Posted by skipjack View Post
Check your diagram with the teacher. If the diagram is correct, the problem is unfairly difficult. See this discussion.

Attachment 9320

In the diagram above, the angles are 32° and 18°, but the discussion above indicates these values are only approximately correct.
This is so hard, is there any easier way to do it? Because we still didn't learn half of these stuff
Ariel4 is offline  
November 23rd, 2017, 03:36 AM   #4
Global Moderator
 
Joined: Dec 2006

Posts: 18,248
Thanks: 1439

There isn't an easier way for this problem. However, I doubt that your teacher intended to set such a hard problem.
skipjack is offline  
November 23rd, 2017, 12:09 PM   #5
Newbie
 
Joined: Nov 2017
From: Serbia

Posts: 6
Thanks: 0

Oh, I guess that's the case then. Can someone help me to understand how to solve this problem step by step? I know I have the answer, but it's to rush up for me. If someone can help me with step by step how-to-do, I will be very thankful.

Last edited by skipjack; November 23rd, 2017 at 06:36 PM.
Ariel4 is offline  
November 24th, 2017, 04:38 PM   #6
Math Team
 
Joined: Oct 2011
From: Ottawa Ontario, Canada

Posts: 11,074
Thanks: 722

How in hell is a student suppose to learn from those
convoluted equations shown at "Cut the Knot"?!

Actually easy "going the long way".
I'll use F instead of your "O"; hate using O.

Let AB = 1

TriangleABF: Calculate AF (Sine Law)
AF = SIN(20) / SIN(130) = ~.446476

TriangleABF: Calculate BF (Sine Law)
BF = (SIN(30) / SIN(130) = ~.652270

TriangleAEF: Calculate EF (Sine Law)
(notice that triangle AEF is isosceles)
EF = AF * SIN(50) / SIN(80) = ~.347296

TriangleBDF: Calculate DF (Sine Law)
DF = BF * SIN(60) / SIN(70) = ~.601534

TriangleDEF: Calculate DE (Cosine Law)
DE = SQRT[DF^2 + EF^2 - 2*DF*EF*COS(130) = ~.866666

TriangleDEF: Calculate angle DEF (Sine Law)
angleDEF = ASIN[DF*SIN(130)/DE] = ~32.122012

angle EDF = 180 - 130 - angle DEF = ~17.877987

Methinks that triangle is perfect in order for students
to learn about Sin/Cos laws.

Last edited by skipjack; November 24th, 2017 at 09:18 PM.
Denis is offline  
November 24th, 2017, 04:59 PM   #7
Senior Member
 
Monox D. I-Fly's Avatar
 
Joined: Nov 2010
From: Indonesia

Posts: 1,530
Thanks: 120

Math Focus: Trigonometry and Logarithm
Quote:
Originally Posted by Denis View Post
I'll use F instead of your "O"; hate using O.
Why do you hate using O? Just curious.
Monox D. I-Fly is offline  
November 24th, 2017, 05:12 PM   #8
Math Team
 
Joined: Oct 2011
From: Ottawa Ontario, Canada

Posts: 11,074
Thanks: 722

Looks too much like a zero.
Similarly hate using I : looks like one.
Denis is offline  
November 24th, 2017, 06:03 PM   #9
Senior Member
 
Joined: Oct 2013
From: New York, USA

Posts: 573
Thanks: 79

Quote:
Originally Posted by Denis View Post
(notice that triangle AEF is isosceles)
That shows that the diagram isn't to scale. In a diagram drawn to scale with the congruent angles being smaller than the other one (50, 50, and 80 in this case), the shortest side is in between the two congruent angles. EO (what you called EF) looks like the shortest side, but AO (what you called AF) is in between the congruent angles.
EvanJ is offline  
November 24th, 2017, 07:06 PM   #10
Math Team
 
Joined: Oct 2011
From: Ottawa Ontario, Canada

Posts: 11,074
Thanks: 722

Well, with top angle = 20, the triangle is a long skinny minny;
so the whole shebang is way outta scale!!
Denis 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.