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October 01, 2025, 04:37:11 pm
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Author Topic: TyErd's questions  (Read 42758 times)  Share 

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kenhung123

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Re: TyErd's questions
« Reply #270 on: June 14, 2010, 06:41:19 pm »
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huh?? Not sure what that question is asking
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TyErd

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Re: TyErd's questions
« Reply #271 on: June 14, 2010, 06:49:07 pm »
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Yeah im not quite sure either, its question 2 in essentials 10G
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the.watchman

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Re: TyErd's questions
« Reply #272 on: June 14, 2010, 07:17:21 pm »
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Well, let D be the distance between a point on and

Then, using the distance formula:



The x-value(s) which give the minimum value of D are the x-values of the required points :)
« Last Edit: June 14, 2010, 07:27:41 pm by the.watchman »
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m@tty

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Re: TyErd's questions
« Reply #273 on: June 14, 2010, 07:19:09 pm »
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It is asking for the point where the connecting line segment is as small as possible.

A point on the line can be given as .

The connecting line will be of length

Then find the minimum of this function and find the coordinates of the point on the parabola.
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TyErd

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Re: TyErd's questions
« Reply #274 on: June 14, 2010, 08:19:49 pm »
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So you differentate : make it equal zero then find the x values?
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the.watchman

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Re: TyErd's questions
« Reply #275 on: June 14, 2010, 08:40:14 pm »
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Quote from: TyErd on June 14, 2010, 08:19:49 pm
So you differentate : make it equal zero then find the x values?


Yes, and make sure you determine/prove local mins using a gradient table :)

EDIT: By chance, I noticed that this is my 999th methods post... :P
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TyErd

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Re: TyErd's questions
« Reply #276 on: June 14, 2010, 08:44:57 pm »
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Okay so far I have this:



How do I simplify it further to find x?
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Blakhitman

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Re: TyErd's questions
« Reply #277 on: June 14, 2010, 08:46:47 pm »
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Well the numerator must equal 0.
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the.watchman

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Re: TyErd's questions
« Reply #278 on: June 14, 2010, 08:47:25 pm »
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Quote from: TyErd on June 14, 2010, 08:44:57 pm
Okay so far I have this:



How do I simplify it further to find x?

In this scenario, you can just multiply both sides by the denominator, so it's

(Don't be worried about removing solutions, the denominator can't be equal to zero anyway :P)

EDIT: Lol, 1000 MM posts :D
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TyErd

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Re: TyErd's questions
« Reply #279 on: June 14, 2010, 08:53:13 pm »
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So you just disregard the denominator altogether when you got something like that equal to zero?

Congrats man 1000 posts, damn im still on 151 haha
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the.watchman

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Re: TyErd's questions
« Reply #280 on: June 14, 2010, 08:55:28 pm »
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Quote from: TyErd on June 14, 2010, 08:53:13 pm
So you just disregard the denominator altogether when you got something like that equal to zero?

Congrats man 1000 posts, damn im still on 151 haha

Yep, if the denominator equaled zero, then the world would have exploded, but it hasn't :P
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Juddinator

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Re: TyErd's questions
« Reply #281 on: June 14, 2010, 10:38:43 pm »
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I've pretty much finished the MC in Chapter 13 of Essentials but there are a few questions in the MC that I don't get..

The graph of crosses the x-axis at the point (4, 0). The gradient at the point
is 1. What is the value of c?

I understand that I have to sub in points (4, 0) but I get stuck finding b. I tried finding the gradient but I was off....

If , then what is equal to?


The straight line cuts the parabola at the point (3, 0). The angle
between the line and the parabola at this point is u. What is tan u?
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kenhung123

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Re: TyErd's questions
« Reply #282 on: June 14, 2010, 10:51:56 pm »
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What does this actually mean?
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moekamo

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Re: TyErd's questions
« Reply #283 on: June 14, 2010, 10:59:56 pm »
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Quote from: kenhung123 on June 14, 2010, 10:51:56 pm
What does this actually mean?

its an addition/subtraction formula, say you wanted to find then you would use the fact that so which you can then simplify with exact values...
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Blakhitman

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Re: TyErd's questions
« Reply #284 on: June 14, 2010, 11:00:21 pm »
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Quote from: Juddinator on June 14, 2010, 10:38:43 pm
I've pretty much finished the MC in Chapter 13 of Essentials but there are a few questions in the MC that I don't get..

The graph of crosses the x-axis at the point (4, 0). The gradient at the point
is 1. What is the value of c?

We  can sub in the given point:
we also know what the gradient is at this point so differentiate:
then substitute x=4 and the gradient equals 1 at this point:

So we have two equations: ----(1) and
----(2)

solve simultaneously and you should get and

Quote from: Juddinator on June 14, 2010, 10:38:43 pm
If , then what is equal to?



Simplify numerator:

Then simplify the whole thing:

I think that's what it's asking for :S, if it wanted the derivative it would be
« Last Edit: June 14, 2010, 11:23:47 pm by Blakhitman »
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