Vastor

Hey guys, Firstly, there 3 chapter that I'm revised related (I thought) with this thread: Electricity, Electromagnetism, Electronics. This would be a long journey(If I have a lot question to ask) So, I hope anyone can give me some intuition for me to solve my confusion. let's get to the first doubt, it's about voltage in series circuit and the nature of voltage itself. based on Textbook, Voltage = "The potential difference between two points is the work done in moving one coulomb from one point to another." This give me a thought of that "I can put Voltage as a 'potential energy' in a circuit, but I wonder how that happen?(my first question)" for the Potential difference in series circuits, I got this one diagram(from the textbook) thus, in one of its "note" I found this, Description: The potential difference between two points in a a circuit is the potential drop from the point of higher potential to the point of lower potential. Figure shows an example where the potential at p is the highest and the potential at r is the lowest. After a while of thinking about these part, I eager to discover more about voltage, there something in my mind that is un-confirmed, yet. Based on the figure below. I'm putting an "imaginary Voltmeter" and put on a wild guess of its value, so can anyone confirm my thought on this?! thnx.

after read this post, you are convincing me to re-read the tutorial once again, until I see how you solve the question. Expected! it's just a problem of mine dealing with denominator that have addition/subtraction symbol. How do you actually factor it? I mean, if me use that method, it should be a wild guess only. About "my method", well, actually I'm just filling the current rules to show my trials, so that people can see where I'm stuck, I'm using derivative for the #2 post in the link above(The Tutorial of Differentiation) where it use some sort of calculation to remove its denominator so that it can move variable "h" to the limit, "0". because of my frustration with the denominator and my un-complete understanding of the Differentiation itself, I give a try to apply the method, thus end up here. P.S. I can solve the second question where [math] \lim_{n \to 0} \frac{n^2 - 2n}{n} [/math] , thnx for not having the silly (+/-) in its denominator Can anyone teach / give a link on how to use L'Hopital's rule, interesting. I'm new to calculus so can't really grasp anything from wikipedia, wolfram alpha, etc... thnx.

sincerely, I don't know what I'm doing with the limit. but finding a value for (something) / 0 is just impossible. ahah, probably that, I just don't know where to start to solve the equation.

Hey guys, There something that I can't digest in this chapter: Differentiation I understood the concept, but I just become confuse either for it symbol, calculation, or maybe I'm missing some concept here. Well, I'm actually talking about the calculation in a book I read. Example 1 Given that [math] y = 3x^2 + 4x - 6 [/math], find [math] \frac{dy}{dx}[/math] using the first principle Solution: Given that [math] y = 3x^2 + 4x - 6 [/math] (1) then, [math] y + \delta y = 3(x + \delta x)^2 + 4(x + \delta x) - 6 [/math] (2) (2) - (1): [math]\delta y = [3(x + \delta x)^2 + 4(x + \delta x) - 6] - 3x^2 - 4x + 6 [/math] [math]\delta y = 3x^2 + 6x\delta x + 3(\delta x)^2 + 4x + 4\delta x - 6 - 3x^2 - 4x + 6 [/math] [math]\delta y = 6x\delta x + 3(\delta x)^2 + 4\delta x [/math] Divide both sides by [math] \delta x [/math] [math] \frac{\delta y}{\delta x} = 6x + 3\delta x + 4 [/math] [math] \frac{dy}{dx} = \lim_{\delta x \to 0} \frac{\delta y}{\delta x} [/math] [math] \frac{dy}{dx} = \lim_{\delta x \to 0} (6x + 3\delta x + 4) [/math] [math] \frac{dy}{dx} = 6x + 4 [/math] But, when I give my try to solve one of the question... Find the value of [math] \lim_{n \to -1} \frac{n^2 - 1}{n + 1} [/math] [math] y = (n^2 - 1)(n + 1)^-1 [/math] [math] y + \delta y = [(n+\delta n)^2 - 1] [n + \delta n + 1] ^-1 [/math] [math] y + \delta y = \frac{n^2 + 2n\delta n + \delta n^2 - 1}{n + \delta n + 1} [/math] [math] \delta y = \frac{n^2 + 2n\delta n + \delta n^2 - 1}{n + \delta n + 1} - \frac{n^2 - 1}{n + 1} [/math] well, I think I'm just not good in fraction or actually I don't understand why I'm coming to this step actually(probably just follow from the given example) hope anyone can give a hand, thank you. EDIT: btw, the answer is = -2

EDIT: Aww, nvm edit2: AJS, should have put 3. multiply with frequency 4. add them all together... etc... I'm confused out of your word actually....

k, lemme try [math]\sigma^2 = \frac{\sum(x-\overline x)^2}{N}[/math] [math]\sigma^2 = \frac{\sum(x-2)^2}{21}[/math] from here, where I assume "x = individucal data point", can you clarify more what is this? I mean the "Number of children per family" or "number of families" etc...

Hey guys, The table above shows the distribution of families with the number of children in the familes. Find (a) the range (done = 4) (b) the interquartile range (done = 3.5) © the variance (nope) (d) the standard deviation (nope) http://www.mathsisfu...-deviation.html conceptually it's understood! but, why: for Variance of a set of ungrouped data [math] \sigma^2 = \frac{\sum(x-\overline x)^2}{N} [/math] or [math]\frac{\sum x^2}{N} - (\frac{\sum x}{N})^2[/math] what is the difference? in my book it tells nothing. -..-" when I tried the second formula it's wrong, for the first formula, I don't know how to use, what is summation symbol precedence compare to multiply/divide?

I'm not understand how this universe is evidence for existence of God that said by the creationist! but at the same time, I can't understand what is evidence / proof also? can anyone give an insight of what this thing is? in other words, how can something be an evidence or not?

hey guys, The table below shows the distribution of marks obtained by a group of students in a Physics test. Construct a cumulative frequency table and draw its ogive, Using the ogive, estimate (a) the median mark, (b) the upper quartile mark, © the percentage of students who obtained more than 60 marks I do calculation rather than construct the cumulative frequency table and draw the ogive, but the answer I got is 49.875, the answer given is (51) same happen for (b) question, I got 70 instead of 65.5("real" answer) does calculation missed that much from the ogive itself?

huh?! you make me lost with that high level of math.... xD

hey guys, The table below shows a set of numbers arranged in descending order where n is a positive integer. (a) Express the median of the set of numbers in terms of n. (DONE) (b) Find the possible value of n. (HOW?) © Using the values of n obtained in (b), find the possible value of the mode (this may be solved when (b) solved)

that's why! distance = [math]\sqrt{(x_1- x_2)^2 + (y_1 - y_2)^2} [/math] where n:m is ratio, [math]m(distance_{AP}) = n(distance_{BP}) [/math] [math]m(\sqrt{(x - x_1)^2 + (y - y_1)^2}) = n(\sqrt{(x - x_2)^2 + (y - y_2)^2}) [/math] right?!

so, (3+7) / 2 = 5 does that all needed to find every first / third quartile in un-group data?

hey guys, the question says... A set of numbers x, 7, 11, 5x has a mean of 9. Find the values of x and the first quartile. firstly, I got x = 3, which is right. but I got problems with finding the first quartile. btw, the answer is 5. so, what does need to be done to find the first quartile in an ungroup data, or does the answer given is wrong??? find quartile in group data seems to be easier... ;O

do you mean n^2(distance_AP)^2 = m^2(distance_BP)^2 ? I think I understand now... tyvm

ahah! now I remember what to reply about the real problem, well I'm talking about the respond from the commenter of the pic itself what I see is that they(most if not all) interpret it as:- 6 / 2(1+2) but, they say "solve bracket first", make it 6 / 6 which is somehow ridiculous, at first I laugh how this poorly calculated, then there so many people supported it which either a. my algebra still sucks. b. their algebra(who telling "solve bracket first") are the one who sucks. what I understand, solving "inside the bracket" =/= "outside the bracket", where when "outside the bracket", it just mean to be multiplication/division.

ouch, I'm totally lost on what you are trying to say, why don't you just go on more with "circles and their functions", btw, why not re-post the "bugged text" ??? thnx

hey guys, there still something that I'm not quite understand on how to calculate locus. this actually help something on intuitive of the locus from a fixed point but not explain much about locus(x, y) from two fixed point, (x1, y1) and (x2, y2), based on ratio of m:n, where the equation is:- [math] \frac{\sqrt{(x - x_1)^2 + (y - y_1)^2}}{\sqrt{(x - x_2)^2 + (y - y_2)^2}} = \frac{m}{n} [/math] can anyone explain more about this?

not looking for much discussion about the order itself, but seriously, same company put two different answer(different order of calculation) on their calculator? anyway, we all know that it was meant to be from left to right, right? never thought this kind of simple algebra would end up to be so complicated

so, wolfram alpha is un-reliable too? http://www.wolframalpha.com/input/?i=6%2F2%281%2B2%29 oh, btw, wat make the multiplication "must" happen before division?

I don't know why people claim fx-570MS is right (most of these guys tell that their teachers said so ) , I mean:- (translated from my comment there) ‎9 is right... proof : ab = a * b, so 6 / 2(3) = 6 / 2 * 3 = 9. (translated from my comment there) so guys, which one is right?

hey guys, because Google no help for now, I think I can't help but ask here... Given that the points A(3, 5), B(6, 2), C(5, -1) and D(p, q) are the vertices of a parallelogram, find the values of p and q. My trial:- I'm assuming AB = CD, so I calculate the distance of line AB (using phytaghoras theorem) [math] AB = \sqrt{8} [/math] I'm assuming BC = AD too [math] BC = \sqrt{10} [/math] ok, I'm clarifying that I'm clueless help anyone?

wow, never thought it would be so hard to search for this on the net... but, atleast it would be a good start to explain the whole equation then... EDIT:- Eureka! after tried it with multiple calculation, I found the intuitive behind the formula itself. if [math] P_1M : MP_2 = 2 : 1 [/math] [math] x_M = x_1 + \frac{2}{3}(x_2 - x_1) [/math] which in other words [math] ("target" x-value) = ("start" x-value) + \frac{ratio of P_1M}{ratio sum}(("end" x-value) - ("start" x-value)) [/math] where:- - when, the "end" x-value minus the "start" x-value, we get the distance between the x-value which is from "start" to "end" of line segment. - the distance times by the ratio related to the line divide by sum of ratio will produce a distant between the "start" point and "target" point. - the distance from "start" to "target" point used to sum with the "start" point to obtain the x-value of the "target" point. thnx everyone ooo wait, I solve this myself, should check out google first next time

heyy guys, there is 1 equation for the point [math](x_p, y_p)[/math] which divides PQ in the ratio m:n, where [math]P(x_1, y_1)[/math] and [math]Q(x_2, y_2)[/math]. [math](x_p, y_p) = (\frac{nx_1 + mx_2}{m + n}, \frac{ny_1 + my_2}{m+ n})[/math] which if specified for the x-axis only... [math] x_p = \frac{nx_1 + mx_2}{m+n}[/math] [math] x_p(m+n) = nx_1 + mx_2[/math] if we put this into variable K [math] K = (x_p)* (m+n) [/math] then K = (horizontal value of the point) * (sum of ratio) so, what is K? why does it must be equal to calculate between the x point?, did I label each variable right?