In need of a throughout explanation of the following problem:

SmellyMan · 2011-10-10 04:45:08

(sqrt(2)/2 +1)/(-sqrt(2)/2 - 1/2)

Wolfram Alpha shows the result is -sqrt(2), doesn't matter what I do it doesn't seem like I can get the exact result...

Any help, please? ^^

Last edited by SmellyMan (2011-10-10 04:47:29)

anonimnystefy · 2011-10-10 05:03:40

hi SmelyMan

is this what you want:

if it is then wolfram is right!

Last edited by anonimnystefy (2011-10-10 05:08:54)

SmellyMan · 2011-10-10 05:06:21

anonimnystefy wrote:

hi SmelyMan
is this what you want:

This is exactly what I am trying to solve!

I couldn't put it into mathematical form as I'm not yet used to the interface and the commands, so excuse me for this mess I made.

Last edited by SmellyMan (2011-10-10 05:12:40)

bobbym · 2011-10-10 05:16:13

Hi;

anonimnystefy · 2011-10-10 05:17:40

here's how you solve it:

if you got the answer from a book then it is probably wrong,or you just looked at the wrong answer.

Last edited by anonimnystefy (2011-10-10 05:18:42)

SmellyMan · 2011-10-10 05:28:31

Thank you very much, I was having so much trouble on my own, I was solving it by anonimnystefy's way, but I probably miscalculated something and just made a bigger mess.

Thank you once again, these angle problems are annoying and you can never be sure of what the right solution can be .

Cheers!

bobbym · 2011-10-10 05:29:52

Math annoying? You are kidding right?

SmellyMan · 2011-10-10 05:32:37

bobbym wrote:

Math annoying? You are kidding right?

It was a remark I made about such problems, where you can never be sure if you calculated it right.

I do not find math annoying at all, and I do realise you made a little personal joke there.
But, admit it, in your early years you often found math annoying when you didn't understand something

Last edited by SmellyMan (2011-10-10 05:47:37)

Bob · 2011-10-10 05:44:35

hi Smellyman

where you can't never be sure if you calculated it right.

But you can with high probability of not missing an error.

Evaluate the starting expression to a decimal result.

Evaluate again at any step where you are in doubt.

If you get the same answer, it is very likely you have made correct steps.

If the answers are not the same, you know you've made a mistake.

You can use the same technique to check algebraic steps.

Choose different values for each variable and evaluate the expression at each step.

It is wise not to choose 0 or 1 as their effect on the calculation may not reveal an error.

Bob

Last edited by Bob (2011-10-10 05:47:56)

SmellyMan · 2011-10-10 05:47:16

bob bundy wrote:

hi Smellyman
where you can't never be sure if you calculated it right.
But you can or at least, with high probability.
Evaluate to a decimal the starting expression.
Evaluate again at any step where you are in doubt.
If you get the same answer, it is very likely you have made correct steps.
If it doesn't, you know you've made a mistake.
You can use the same technique to check algebraic steps.
Choose different values for each variable and evaluate the expression at each step.
It is wise not to choose 0 or 1 as their effect on the calculation may not reveal an error.
Bob

What I meant by confusing the right answer is I can never be sure if the number is positive or negative. At least with reference angles, they're just pain for me to deal with...

Also, for example, when you're writing on the test, you usually don't have the time to check your answers. Sure, when you're learning and doing exercises, I always try to get the right answer, but when you're in a hurry, you'll usually go with the first answer you get, unless you sense there is something REALLY, REALLY wrong.

Last edited by SmellyMan (2011-10-10 05:50:11)

Bob · 2011-10-10 05:50:38

Did this question start with sines and cosines by any chance?

Bob

SmellyMan · 2011-10-10 05:53:09

bob bundy wrote:

Did this question start with sines and cosines by any chance?
Bob

It did, the original task I had was:

(cos(7pi/4) - sin(-9pi/2)) / (sin31pi/4 + cos(-16pi/3))

Bob · 2011-10-10 05:57:37

OK. But you can still evaluate this to get the initial value.

Have you had a look at

http://www.mathsisfun.com/algebra/trigo … index.html

There is a wealth of excellent help here.

Bob

Last edited by Bob (2011-10-10 05:58:11)

bobbym · 2011-10-10 06:00:24

Hi SmellyMan;

But, admit it, in your early years you often found math annoying when you didn't understand something

Early years! I still find it that way. But I found a trick.

SmellyMan · 2011-10-10 06:04:53

bobbym wrote:

Hi SmellyMan;
But, admit it, in your early years you often found math annoying when you didn't understand something
Early years! I still find it that way. But I found a trick.

Could you share this little trick of yours?

bob bundy wrote:

OK. But you can still evaluate this to get the initial value.
Have you had a look at
http://www.mathsisfun.com/algebra/trigo … index.html
There is a wealth of excellent help here.
Bob

Thank you, I'll be sure to check this out!

Last edited by SmellyMan (2011-10-10 06:05:26)

bobbym · 2011-10-10 06:17:20

Most math instruction quickly teaches the student the folly of treating math as an experimental science. They discourage numerical experimentation, the kind bob bundy is recommending. Students quickly come to believe that mathematics has nothing to do with arithmetic.

You will see if you have not already, olympiad level problem solvers who do not know how to plug in to test. They post complicated inequalities that are false. The concept of a counter example is unknown to them.

If I have survived against their superior talent it is only due to the fact that I can plug in, they can not. Sound farfetched?

SmellyMan · 2011-10-10 06:20:38

bobbym wrote:

Most math instruction quickly teaches the student the folly of treating math as an experimental science. They discourage numerical experimentation, the kind bob bundy is recommending. Students quickly come to believe that mathematics has nothing to do with arithmetic.
You will see if you have not already, olympiad level problem solvers who do not know how to plug in to test. They post complicated inequalities that are false. The concept of a counter example is unknown to them.
If I have survived against their superior talent it is only due to the fact that I can plug in, they can not. Sound farfetched?

If I understood you right, people are taught too exact about maths and are not left out on their own to experiment all possible ways to solve a problem?

Last edited by SmellyMan (2011-10-10 06:23:12)

bobbym · 2011-10-10 06:27:36

Somewhat, if 25 of them come out of a course all 25 of them solve ever problem in the same way. Stump one you stump them all. There is a famous story by Richard Feynman along these lines.

SmellyMan · 2011-10-10 06:33:49

bobbym wrote:

Somewhat, if 25 of them come out of a course all 25 of them solve ever problem in the same way. Stump one you stump them all. There is a famous story by Richard Feynman along these lines.

The only way I could see this working is if I took more time to actually study all of the possible ways, or at least the more sensible ones, but the truth is, with all other classes I have I simply don't have the time to focus just on the math alone, and the knowledge teachers teach us is very limited.

Ofcourse, I'm a curious person, always trying to learn more, but it eventually gets to the point where I have to sit down, study for a few hours and not even realise I have 15 other subjects to learn, it's just too much at times.

bobbym · 2011-10-10 06:41:54

One day you will settle down on one thing. You will focus on it. Hopefully the education you have received has not done you any permanent damage. At that time you will restructure your mind. Maybe it will be mathematics, maybe not. What you will find is that whatever training you have received will in no way prepare you for your job.

SmellyMan · 2011-10-10 06:52:07

bobbym wrote:

One day you will settle down on one thing. You will focus on it. Hopefully the education you have received has not done you any permanent damage. At that time you will restructure your mind. Maybe it will be mathematics, maybe not. What you will find is that whatever training you have received will in no way prepare you for your job.

Future is the future, I live in the moment, and now, I am busybusybusybusy .

bobbym · 2011-10-10 07:02:19

Very good! Idle hands are the devils workshop. An old Italian proverb!

SmellyMan · 2011-10-10 07:12:50

bobbym wrote:

Very good! Idle hands are the devils workshop. An old Italian proverb!

I must admit I do get lazy quite often though, probably putting a lot of unnecessary work on my hands . Just by stockpiling thing, but I never learn, why are humans like that?

You know you're doing something badly, and you know you should improve, but you don't, what's up with that?!

bobbym · 2011-10-10 07:22:14

I am afraid that never goes away. But if you understand that, I mean deeply, then you will never set unrealistic goals for yourself. You will know that improvement takes time. Lots of time!

SmellyMan · 2011-10-10 07:24:15

bobbym wrote:

I am afraid that never goes away. But if you understand that, I mean deeply, then you will never set unrealistic goals for yourself. You will know that improvement takes time. Lots of time!

Well my original plan is to establish a chocolate factory!
And go on from there ^.^

Math Is Fun Forum

#1 2011-10-10 04:45:08

In need of a throughout explanation of the following problem:

#2 2011-10-10 05:03:40

Re: In need of a throughout explanation of the following problem:

#3 2011-10-10 05:06:21

Re: In need of a throughout explanation of the following problem:

#4 2011-10-10 05:16:13

Re: In need of a throughout explanation of the following problem:

#5 2011-10-10 05:17:40

Re: In need of a throughout explanation of the following problem:

#6 2011-10-10 05:28:31

Re: In need of a throughout explanation of the following problem:

#7 2011-10-10 05:29:52

Re: In need of a throughout explanation of the following problem:

#8 2011-10-10 05:32:37

Re: In need of a throughout explanation of the following problem:

#9 2011-10-10 05:44:35

Re: In need of a throughout explanation of the following problem:

#10 2011-10-10 05:47:16

Re: In need of a throughout explanation of the following problem:

#11 2011-10-10 05:50:38

Re: In need of a throughout explanation of the following problem:

#12 2011-10-10 05:53:09

Re: In need of a throughout explanation of the following problem:

#13 2011-10-10 05:57:37

Re: In need of a throughout explanation of the following problem:

#14 2011-10-10 06:00:24

Re: In need of a throughout explanation of the following problem:

#15 2011-10-10 06:04:53

Re: In need of a throughout explanation of the following problem:

#16 2011-10-10 06:17:20

Re: In need of a throughout explanation of the following problem:

#17 2011-10-10 06:20:38

Re: In need of a throughout explanation of the following problem:

#18 2011-10-10 06:27:36

Re: In need of a throughout explanation of the following problem:

#19 2011-10-10 06:33:49

Re: In need of a throughout explanation of the following problem:

#20 2011-10-10 06:41:54

Re: In need of a throughout explanation of the following problem:

#21 2011-10-10 06:52:07

Re: In need of a throughout explanation of the following problem:

#22 2011-10-10 07:02:19

Re: In need of a throughout explanation of the following problem:

#23 2011-10-10 07:12:50

Re: In need of a throughout explanation of the following problem:

#24 2011-10-10 07:22:14

Re: In need of a throughout explanation of the following problem:

#25 2011-10-10 07:24:15

Re: In need of a throughout explanation of the following problem:

Board footer