October 27th, 2017, 06:46 PM  #1 
Senior Member Joined: Jan 2017 From: US Posts: 113 Thanks: 6  Construct a TwoColumn Proof
Hello, Can anyone help me with this question? Given that m ∠2 = (4x + 20)° and m ∠3 = (x − 10)°, prove that m ∠2 = 156° by constructing a twocolumn proof. You must include a twocolumn proof with a column for statements and a column for reasons that justify your statements. 
October 27th, 2017, 07:04 PM  #2 
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,881 Thanks: 1088 Math Focus: Elementary mathematics and beyond 
Sure, we can help. What have you done to solve this so far? Where are you having difficulty?

October 27th, 2017, 07:14 PM  #3 
Senior Member Joined: Jan 2017 From: US Posts: 113 Thanks: 6 
I'm having difficulty with the whole "proving it" thing.

October 27th, 2017, 07:22 PM  #4 
Senior Member Joined: Jan 2017 From: US Posts: 113 Thanks: 6 
This is about as far as I've gotten. Sooo if anyone has any advice they'd like to offer, it'd be appreciated.

October 27th, 2017, 07:25 PM  #5 
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,881 Thanks: 1088 Math Focus: Elementary mathematics and beyond 
Statement: (4x + 20)$^\circ$ + (x  10)$^\circ$ = 180$^\circ$ Reason: the sum of adjacent angles on a straight line is 180$^\circ$ Can you continue? (You might have a different way of stating what I said above in the "Reason") 
October 27th, 2017, 07:35 PM  #6 
Senior Member Joined: Jan 2017 From: US Posts: 113 Thanks: 6  So then the answer to that would be 5x + 10? So could you find x by doing (4x+20)= 156, since angle 2 is 156 degrees?

October 27th, 2017, 07:42 PM  #7 
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,881 Thanks: 1088 Math Focus: Elementary mathematics and beyond 
You're trying to prove angle 2 is 156 degrees, so you can't use that. You are not trying to find x, though you have to do that as an intermediate step. If you have 4x + 20 + x  10 = 180, what is x? 
October 27th, 2017, 08:00 PM  #8  
Senior Member Joined: Jan 2017 From: US Posts: 113 Thanks: 6  Quote:
(4(34)+20) + (3410) is 180. So then that proves it, right? Because it proves the first part of the statement is 156? Last edited by skipjack; October 27th, 2017 at 09:49 PM.  
October 27th, 2017, 08:07 PM  #9 
Senior Member Joined: Jan 2017 From: US Posts: 113 Thanks: 6 
Ok, I got it. Thanks!

October 27th, 2017, 09:53 PM  #10 
Global Moderator Joined: Dec 2006 Posts: 19,866 Thanks: 1833 
That's mathematically correct, but your calculations (that x = 34, etc.) presumably should be done in detail in twocolumn format.


Tags 
construct, proof, twocolumn 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Need help with proof on column space  123qwerty  Linear Algebra  2  July 22nd, 2016 10:41 AM 
question involving matrix row column rank proof  maximus101  Algebra  1  December 31st, 2015 04:45 PM 
3x4 Matrix with all 0's in the first column  84grandmarquis  Linear Algebra  3  September 22nd, 2013 05:13 AM 
triangle 2 column proof question  alquix  Algebra  3  April 30th, 2013 09:19 PM 
Geometry: Two column proof for this.  rileymicks  Geometry  1  December 8th, 2012 01:53 AM 