Setting Up an Advanced Mathematics Equation

[voko]

Not only that, you did not apply the distr. property to A's.

 

[Medgirl314]

Right! Take five-billion: (360-2A)=(360-4A)
That should look better.

 

[Medgirl314]

Wait, nope. It doesn't make sense.

 

[Medgirl314]

I forgot the 104. Maybe this will work. (360-2A)=(360-4A)+104

 

[voko]

This is better :)

 

[Medgirl314]

Finally. It astonishes me that I had less trouble with Honors Physics the other day than with basic algebra.
(360-2A)=(464-2A)

 

[Medgirl314]

Oops. (360-2A)=(464-4A)

 

[Medgirl314]

Doesn't seem right. Should I subtract the 104 instead of adding?

 

[Medgirl314]

But that would yield (360-2A)=(256-4A), which also seems wrong.

 

[Medgirl314]

Oh! I forgot P.E.M.D.A.S.

 

[Medgirl314]

(180-a)=(90-a)+104

 

[voko]

I forgot the 104. Maybe this will work. (360-2A)=(360-4A)+104

Note that 360 on both sides just cancel each other out.

 

[Medgirl314]

Right. Duh. Oops. But then it would seem to be just (2A)=(4A)+104. I did something wrong there.

 

[Medgirl314]

Unless the answer is 52 degrees.

 

[Medgirl314]

I think it is, now that I plus it in.

 

[voko]

In #63, you lost minus signs. Bad.

In #64, you got the correct answer, seemingly by magic.

This has been a looong thread. I suggest you post the entire solution in one concise post.

 

[Medgirl314]

I checked the answer key, it is! Thank you for your time and patience. :-)

 

[Medgirl314]

Yes, I lost them, but added them back into my equations in my head, and divided.

 

[Medgirl314]

Okay, here is the solution we came up with.

2S=4c + 104=A
S=180-A
C=90-A

2(180)=4(90-A)+104
(360-2A)=(360-4A)+104
(-2A)=(4A)+104
2A=104
A=52

 

[voko]

Okay, here is the solution we came up with.

2S=4c + 104=A

Ah oh. What is =A doing here, again?

(360-2A)=(360-4A)+104
(-2A)=(4A)+104

Another minus is lost. You should go more frugally about them.

 

[Medgirl314]

I though it was in the original equation before we substituted. So what should I do with the negative sign? I thought adding -2A to 4A to obtain 2A canceled it out.

 

[Medgirl314]

*thought

 

[Medgirl314]

Oh, actually, I thought that when we canceled out the 360s, we lost one, and when we subtracted 2A from 4A we lost one.

 

[voko]

When you lose the 360s, lose nothing else.

 

[Medgirl314]

Okay. Would you mind explaining where the negative signs go? I'm over-complicating it.

 

[voko]

They do not go anywhere. They stay put. If you want to get rid of a minus sign, you do not just drop it. Instead, you move the entire term the minus sign is attached to to the other sign of the equation, where the minus sign is replaced with the plus sign.

It looks like you a need an algebra refresher. You won't succeed in physics unless you can manipulate algebraic expressions effortlessly.

 

[Medgirl314]

I assumed that since a negative number plus a negative number is also a negative number, I had to find some other way to move them. Thanks for helping! Yes, I need to brush up on algebra as I took a different mathematics course last year, but it is coming back to me as I take Algebra 2 and Precalculus. :-)

Did you author Microwave Physics by any chance?

 

[voko]

I assumed that since a negative number plus a negative number is also a negative number

No, this is not correct, which is seen, for example, from -1 + 2 = 1. You are confusing that with multiplication, where indeed (-1)x(2) = (-2).

Yes, I need to brush up on algebra as I took a different mathematics course last year, but it is coming back to me as I take Algebra 2 and Precalculus. :-)

You may want to go through your course materials/textbook for Algebra 1, because these will assume you have mastered the previous material; unfortunately, you knowledge of that seems patchy.

Did you author Microwave Physics by any chance?

Nope.

 

[Medgirl314]

I got my negative plus a negative equals a negative from elementary math sources, such as my Algebra book and websites dedicated to algebra and the like. Perhaps I am confusing this elementary rule with a different one designed for equations like this one.

You're probably right.I know a good bit from Algebra one, but certain types of problems throw me off. I am constantly reviewing algebraic rules. It helps that I have review for the first few lessons in my books. I'm pretty good when I only have numbers to deal with, but when it's disguised as a word problem, it throws me off a bit.

Oh, your name on here is the author's last name.

Thanks again for the help!

 

[voko]

In physics, you have to convert words into symbolic equations, and manipulate symbols rather than numbers. This is unavoidable if you want good grades. I advise that you should post a message to the academic guidance section on this forum, asking what books and/or websites could help you master these skills.

 

[Medgirl314]

I'm getting better at it, as there are many word problems in my courses. My physics course builds upon itself, and my teacher is extraordinary helpful, so I'm getting good grades. Thanks for your input! I have several resources I use, but I will remember this forum if I need additional ones for my classes.

 

[kastelian]

Found interesting that this problem even does not require algebra more than writing 2s=4c+104 and divide by 2. It gives s=2c+52. Drawing a picture makes it visible that unknown angle must be 52 :)

 

[Medgirl314]

Well. You should stick around. I think I came up with that on the first page, but we made it complicated by adding other equations.I should have thought to keep that answer! Thank you for doing what it took us about 75 posts to do in one! :-D And being so polite about pointing out which should have been obvious to me.xD

 

[kastelian]

Yeah, but you need a picture to show that. It's not obvious. Sticking to algebra is a sure way to find a solution.

 

[Medgirl314]

A picture would be helpful-but your ingenious solution states the answer in it, if I am not mistaken. You'reYou're right, algebra is reliable. Thank you again!