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Math people, simple algebra, is this person showing their work?(real)

Posted on 3/11/16 at 9:26 pm
Posted by Kujo
225-911-5736
Member since Dec 2015
6015 posts
Posted on 3/11/16 at 9:26 pm


Basically the old solving for two variables A and B

sin30=cos60=.5
sin60=cos30=.866

(Fx): -.5A+.866B=0
(Fy): .866A+.5B=100

A=.866B/.5

.866(.866B/.5)+.5B=100

2B=100

B=50
A=86.6

pretty easy, standard algebra

But is this person actually showing that? My question is in regards to step 3, while the equation works, I can't figure our how they got to that step.

Everyone knows I'm an idiot, but I'm also tired....can anyone see how they came to that equation?

-.866A+1.5B=0


This post was edited on 3/11/16 at 9:38 pm
Posted by TheIndulger
Member since Sep 2011
19239 posts
Posted on 3/11/16 at 9:27 pm to
Please stop you're giving me flashbacks
Posted by tduecen
Member since Nov 2006
161244 posts
Posted on 3/11/16 at 9:27 pm to
The answer is always C
Posted by Nado Jenkins83
Land of the Free
Member since Nov 2012
59586 posts
Posted on 3/11/16 at 9:28 pm to
Grade your tests. It's your job not mine
Posted by ehidal1
Chief Boot Knocka
Member since Dec 2007
37133 posts
Posted on 3/11/16 at 9:28 pm to
Looks like somebody drew 2 dicks in that graph
Posted by tigerbutt
Deep South
Member since Jun 2006
24561 posts
Posted on 3/11/16 at 9:30 pm to
You obviously do not understand standard algebra.
Posted by ksayetiger
Centenary Gents
Member since Jul 2007
68265 posts
Posted on 3/11/16 at 9:31 pm to
Its pulling 100K

Thats it?


Ot poor
This post was edited on 3/11/16 at 9:32 pm
Posted by Kujo
225-911-5736
Member since Dec 2015
6015 posts
Posted on 3/11/16 at 9:33 pm to
Halp
Posted by motorbreath
New Orleans Saints fan
Member since Jun 2004
6381 posts
Posted on 3/11/16 at 9:34 pm to
Looks more like trigonometry or calculus than standard algebra to me.
Posted by LSUTANGERINE
Baton Rouge LA
Member since Sep 2006
36113 posts
Posted on 3/11/16 at 9:37 pm to
This is trig. Not algebra
Posted by Kujo
225-911-5736
Member since Dec 2015
6015 posts
Posted on 3/11/16 at 9:40 pm to
quote:

This is trig. Not algebra


it's not, forget the sin/cos

2x+3y=100
-4x+8y=24

simple algebra, the subject is statics, but the math on this problem is just algebraic
Posted by Ingeniero
Baton Rouge
Member since Dec 2013
18255 posts
Posted on 3/11/16 at 9:40 pm to
He multiplied both sides of the Fx equation by (.866/.5), so now the equation is -.866A+1.5B=0. He did it so he could solve the system by elimination, since the coefficients of A are the same, with opposite signs now. Weird way to do it but it works.
Posted by bah humbug
Member since Nov 2011
1705 posts
Posted on 3/11/16 at 9:41 pm to
The answer to your question is that the student possibly cheated. Clearly she knew the answer beforehand and then "combined" steps beause she didn't quite know how to correctly get to the answer.
Posted by Armymann50
Playing with my
Member since Sep 2011
17037 posts
Posted on 3/11/16 at 9:41 pm to
quote:

can anyone see
Answer: Who gives a frick
Posted by airfernando
Member since Oct 2015
15248 posts
Posted on 3/11/16 at 9:42 pm to
quote:

is this person showing their work
I don't know about the math, but their is plural.
Posted by LSUTANGERINE
Baton Rouge LA
Member since Sep 2006
36113 posts
Posted on 3/11/16 at 9:46 pm to
quote:

it's not, forget the sin/cos 2x+3y=100 -4x+8y=24 simple algebra, the subject is statics, but the math on this problem is just algebraic


If the student left out sin and cos, would his or her answer still be correct? I really don't know, so I am asking.

Nevermind, I saw sin and cos and hi-tailed it out of here without reading the problem. I see what you are saying
This post was edited on 3/11/16 at 9:49 pm
Posted by MaroonWhite
48 61 69 6c 20 53 74 61 74 65 21
Member since Oct 2012
3689 posts
Posted on 3/11/16 at 9:46 pm to
quote:

He multiplied both sides of the Fx equation by (.866/.5), so now the equation is -.866A+1.5B=0. He did it so he could solve the system by elimination, since the coefficients of A are the same, with opposite signs now. Weird way to do it but it works.


This is what he did. He actually states it in the middle of the diagram.
Posted by CE Tiger
Metairie
Member since Jan 2008
41584 posts
Posted on 3/11/16 at 9:47 pm to
quote:

Looks more like trigonometry or calculus than standard algebra to me.


it's statics. sum of forces in x = 0, sum of forces in y=0
Posted by SurfTide
San Diego, CA
Member since Nov 2015
1658 posts
Posted on 3/11/16 at 9:48 pm to
quote:

Looks more like trigonometry or calculus than standard algebra to me.


It's a simple physics problem which requires trig and algebra to solve. No calculus though (limits, integrals Rieman sums, etc)
Posted by RC
Member since Apr 2009
957 posts
Posted on 3/11/16 at 9:49 pm to
quote:

This is what he did. He actually states it in the middle of the diagram.



Yes, but why? Is that some common core bullshite math they're teaching now?

The way Kujo explained is how I would have worked it.
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