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#1 Help Me ! » order of operations LOGARITHMS » 2015-05-12 06:58:45
- Whizzies
- Replies: 1
Hello!
I've searched the web and I read the rules of logarithms on mathisfun, but I still don't get it!
I try to solve ln 4 - ln 2 + ln 3
I get (first dividing) ln 6 and,
(first multiplication) ln 4/6
What am I doing wrong?
#2 Re: Help Me ! » Trigonometry » 2014-11-28 06:09:23
okay! I think it is best if I just learn the formulas for this, because I see it is more difficult than anticipated. I can follow your reasoning, but I cannot understand it in the sinus graph and sadly that is the way I wanted to see it 
I am now practising a lot with the sine and unit circle to understand it properly. I even found some cool stuff online that will help me out.
Thanks thought for explaining this to me.
#3 Re: Help Me ! » trigonometry the period! » 2014-11-25 04:28:40
I can follow that... but it is too much magic for me atm
#4 Re: Help Me ! » trigonometry the period! » 2014-11-21 21:55:29
Thanks Guys (: I am understanding what it is that I am doing.
Like for example when I mulptiply the sin(x) with 2 I change the distance in respect to the y-axes, hence the period changes. The explanation was very clear Ty
I do have one question though!
In my book it is explained that:
g(2x)=f(x) <=> g(x)=f(x/2)
I understand what happens when you multiply by two, ut I don't understand why it could also be 1/2.
#5 Re: Help Me ! » trigonometry the period! » 2014-11-20 06:55:15
What does y-as mean here?
y axes sorry
#6 Help Me ! » trigonometry the period! » 2014-11-20 06:03:39
- Whizzies
- Replies: 8
Hello,
can someone explain to me the difference between multiplying relative to the y-axes and the period?
so sin (x) period is 2pi
multiply relative to the y-as with 3 than formula would be sin(x/3) and the period (2pi)/3 right?
I always mix them up and I don't know how to deal with it properly... could someone help?
thx
#7 Help Me ! » Trigonometry » 2014-11-20 05:59:36
- Whizzies
- Replies: 2
Hello everybody!
I am stuck with these functions:
It is about trignometry the functions of sine and cosine;
This is the formula for line symmetry: f(a-p)=f(a+p) I can follow the reasoning behind that.
but point symmetry just blows my mind:
f(a-p)-b=b-f(a+p)
Left side and right side
I don't understand it! please help me I can't find this on the net.
#8 Re: Help Me ! » Logarithm which goes first? » 2014-10-10 05:22:28
Why does it not work for x = - 5?
Log is only defined for x>0
log (x+3)
x = -5
log (-5+3) = log (-2)
Log (-2) is not defined.
#9 Re: Help Me ! » Logarithm which goes first? » 2014-10-10 04:42:17
You’ve got as far as
[list=*]
[/*]
[*]
[/list]Now just solve it for x.
Yes, very true. But in the future I have to solve lots and lots of equations, and I'd like to know the basic rules (:
Another question though!
x^2+6x+5 = 0
(x+5)(x+1)=0
x = -5 and x = -1
it does not work for x = -5. Why do we check this with the first formula? (log x+3) and not with the later formula ((x+3)^2)?
#10 Help Me ! » Boolean Algebra » 2014-10-10 04:19:38
- Whizzies
- Replies: 1
Hello all,
I have been googling like hell for some sheets with excersises for boolean algebra and only found this http://web.mit.edu/6.111/www/s2007/PSETS/pset1.pdf
I am searching for more sheets so that I can master this kind of algebra.
Does anyone have some for me?
Thanks!
#11 Help Me ! » Logarithm which goes first? » 2014-10-10 04:17:36
- Whizzies
- Replies: 7
Hello fellow people,
question:
I have learned this:
log (uw) = log u + log w
log (U/W) = log u - log w
log U^2 = 2 log u
My question is this:
2 * log2 (x+3) = log2 (12) - log2 (3) =
log2 (x+3)^2 = log2 (4)
(x+3)^2 = 4
What must go first? Multiply addition or subtraction?
Like 2 * 3 + 4= x, the rules are 2*3 first than add 4.. but how does it work with logaritms?
#12 Re: Help Me ! » The function s(t) =vt what is the variable? » 2014-08-05 19:28:25
hi Whizzies
If it has brackets t, s(t), this is a way of saying that the variables are t and s. You can read it like this:
"s is a function of t; s is determined by multiplying t by v"
In general if s = vt, then all could be variables.
I would have a s,t diagram but it doesn't really matter. A graph is still a graph, if you reverse the axes.
Some people insist that the across axis is the independent variable (ie. you choose the values for it) and the up axis is the dependent variable (ie. you work out its values from the formula or from the graph. But even that isn't compulsory.
http://www.mathsisfun.com/sets/function.html
Bob
I've read that part, I am read a little bit about functions in functions and so on. Math seems to say a lot about formulas and graphs and how they behave, and it is the transition between the formula and graph that I find difficult sometimes. Cause for example if you have an (x,t)-diagram and you take the derivative from it you have speed and if you taak another derivative from the speed you get acceleration. But it is about points, its in that point and you can take differend points and make a graph from it.
you also have functions like:
f(z,y,x) = it is a threedimensional function, but a function with three variables is unsolvable (at least for me at this point) I still have some questions, but I have to think a little and practise a bit to formulate. Thanks for helping (:
#13 Re: Help Me ! » Linear equation? » 2014-08-05 07:02:57
The book is wrong.
Hehe, explain why the book is wrong.
#14 Help Me ! » The function s(t) =vt what is the variable? » 2014-08-04 07:13:47
- Whizzies
- Replies: 2
This function is only valid if the speed is constant. I have a question, I am trying to learn something very basic from the special relativity theorie. You can make an (s,t)-diagram from this function. My question is:
How do you know what is the variable in any given formula? The function s(t)=vt is a given function and the variable is t, but how could you find it out if the formula
was given?And the diagrams what is the difference between a (s,t)-diagram and a (t,s)-diagram? I am taught to write down a (s,t)-diagram, but in the (hand-out; about relativity) they use an (t,s)-diagram.
how how? Ty
#15 Re: Help Me ! » Derivative of Ln(x) » 2014-08-03 23:07:30
hi Whizzies,
'Product rule' is good in English. I would have used 'constant' , but I chose 'fixed number' as I thought it would be easier to understand. That's my doh moment.
In all the books I've seen teaching logs, the log base is shown as a subscript, thus:
I'm glad this has become clear for you.
Bob
Hé Bob,
Yes
this is for the USA and perhaps other countries, but in the Netherlands we use without the dot. I just remembered that there is a small difference in the notation (:Well things turned out okay! Im really happy for all the help (: I still have lots and lots of questions (:
#16 Re: Help Me ! » Derivative of Ln(x) » 2014-08-03 19:09:09
I had a major DÔH moment this morning. I read you previous post and was like... okay... At first it was hard to understand for me, but when I woke up this morning the dôh came.
I did not apply the product rule! (Dunno if it is the same in English as in Dutch and fixed numbers we call a constante) Thank you!
so the proper derivative is:
f(x)=
f'(x)=
but the ln(x) * 0 = 0
#17 Re: Help Me ! » Derivative of Ln(x) » 2014-08-02 07:32:44
Whizzies wrote:the derivative of
Not so. There are two things wrong here:
(1) g is a fixed number, not a variable. So you could replace with k:
and when multiplied by a function of x
(2) But there's another thing here.
Let's suppose that g is a variable so that
You cannot just invert both expressions to get
After all, you know that
but
And I've just noticed a third thing:
is not the same as
Bob
ps Why have I used dy/dx rather than f' ?
Simply that I don't know how to get a dash when using Latex. I'm sure that someone will delight in telling me this, now I've admitted my ignorance, so, thanks in anticipation.
I am sorry Bob Bundy, but I still don't understand. What is the difference between a fixed number and a variable? So the mistake I make is that I approach the fractal as a variable?
#18 Re: Help Me ! » Derivative of Ln(x) » 2014-08-02 02:13:05
Advice: do not trust any book with all your life
Good advice ! I learned it a year ago, though! That is why I am asked it, but it seems that I don't undestand something else.
#19 Re: Help Me ! » Derivative of Ln(x) » 2014-08-02 02:12:03
Your image shows the derivative for ln(x) (natural log base e) and also how to differentiate when the log base is different (say, base g)
You can convert another log base like this:
Take logs in base e
Now you can differentiate using the standard method:
Bob
Heyyy,
we learn that
= f'I don't know if people that go to ''normal'' schools also learn it in the fashion, but I am in a school that compresses 5 years of math in 1 year and I don't really have any basis. I can differentiate and use certain things, but I don't know the real basis (:
The two examples that you portrayed I understand those two.
What my problem is:
http://imgur.com/5H7Gnzv
it says that the derivative of the left side is equal to the right side, but the derivative of
= g. I am sorry I am overthinking this problem and I get stuck
Just now I was thinking what if I differentiated
the answer .. SO I am doing something wrong, but I don't know what!#20 Re: Help Me ! » Derivative of Ln(x) » 2014-08-01 18:00:20
hi Whizzies,
I'm assuming that's a log base 'e'.
So
Bob
I understand what you are doing, but I can't seem to integrate it with my problem (:
I posted a link, so that it is clear for everybody to see, bec I am quite new with latex.
#21 Re: Help Me ! » Derivative of Ln(x) » 2014-08-01 17:58:53
http://imgur.com/5CDcty0
here is a link;
#22 Re: Help Me ! » Derivative of Ln(x) » 2014-08-01 06:43:50
This one is bothering me
it should be just g. The derivative.#23 Re: Help Me ! » Derivative of Ln(x) » 2014-08-01 04:27:20
Hm, it's all mixed up. How is 1/ln(g) * ln(x) = (1/ln(g)) * (1/x) ?
That is my question. What I wrote there comes straight out of the book. What I say about (what I think) is what I think...
It is supposed to be the proof that f(x) = g^log(x) = dy/dx =g^log(x) = 1/(x ln(g)
#24 Help Me ! » Derivative of Ln(x) » 2014-08-01 02:00:26
- Whizzies
- Replies: 18
I had to find the derivative of 3^log (x^3).
In my study book:
g^log(x) = ln(x)/ln(g) = 1/ln(g) * ln(x) = (1/ln(g)) * (1/x) = 1 / (x ln(g)
Well! I understand most of it but I do not understand this.
1 / ln(g) = 1 / ln(g)
In my head:
Ln(g) = 1 /g
1/ln (g) = 1/(1/g) = g
#25 Re: Help Me ! » Trigonometry proof of formula » 2014-08-01 01:56:36
I would recognize a matrice, but I wouldn't know what it is. I will be learning about the compound angles very soon also the formules from Mollweide will I be studying, but I am a bit in time distress!
Radian is not radians? I did mean Gradients, yes! Haha I thought it was 420! But I never used it or have read properly about it. I know that I ask sometimes question that are already explained on the website, but sometimes I am too uncertain if it really is like that (:
Before I started to delve a little bit deeper in the unit circle; I always thought that it were to seperate things, but evidently they are connected with eachother. I still don't understand properly what the function precisely is. I just have to go a little bit deeper and try to make connections and such (:
Feynman did say that, did he not! But I guess one day there will be someone who understand it, and knows it very well! I have a small cursus of the special relativity of Einstein, that I want to absorb, but my teacher said that it would be wiser if I first strenghten my mathematic abilities (: