#1
(again, I've deleted the other maths thread I made to stop spam. this way people will actually see the new question I am asking)

I'm revising and need help with this question;

The curve with equation y = ln 3x crosses the x axis at point P(p,0)

a) sketch the graph of y = ln 3x showing the exact value of p

I did that algabraically instead of sketching and p is 1/3
Then I get to the next question

The normal to the curve at the point Q, with x coordinate q, passes through the origin.
b) Show that x=q is a solution to the equation x^2 + ln 3x


How do you do (b)?
#2
ummm, im not sure how to go about this, but would differentiating and then putting q into the expression you get, then take the negative reciprocal of it, that would give you the gradient of the normal in terms of q. c is 0 as it goes through the origin.

im just throwing an idea at you lol. im not really sure, that seems quite hard.
#3
I think xX_Jimi_Xx has something, but I don't remember derivatives of natural logs.

You just have to figure out the x-coordinate on the graph where the normal goes through the origin, then plug that number into the second equation x^2 + ln 3x (= 0?)
METAR KTIK 040043Z COR RMK TORNADO 1W MOV NE. EVACUATING STATION
#4
eww...
books have knowledge, knowledge is power, power corrupts, corruption is a crime, and crime doesn't pay..so if you keep reading, you'll go broke.

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#5
the derivative of lnx is 1/x

ln3x is also ln3 + lnx.

therefore the derivative of ln3x is also 1/x i think. it is possible im wrong though lol
#9
Hey I have a quick question Logic_Smogic. I was reading in your profile that you are a Physics major and I was wondering what math classes have/will you take in college? Right now I'm a junior in high school and in Calc. 1 and next year I will take Calc. 2 but I was curious what my options are for college as far as math goes.

Don't want to be an actor pretending on the stage
Don't want to be a writer with my thoughts out on the page
Don't want to be a painter 'cause everyone comes to look
Don't want to be anything where my life's an open book

Phish - Waste
#10
Quote by IrishBlues
Hey I have a quick question Logic_Smogic. I was reading in your profile that you are a Physics major and I was wondering what math classes have/will you take in college? Right now I'm a junior in high school and in Calc. 1 and next year I will take Calc. 2 but I was curious what my options are for college as far as math goes.


For me, the story goes like this:

AP Calculus (AB) - High School

College (UW-Madison):
Calculus II
Calculus III (dropped, and started new 'Honors' sequence instead, listed below)

Calculus I (proof-based)
Calculus II (proof-based)
Multi-Variable Calculus and Linear Algebra (proof-based)
Multi-Variable Calculus and Differential Equations (proof-based)
Probability

..and I will likely take courses in Real Analysis and Advanced Algebra (and/or complex).

I've learned a lot of math in my physics courses, though. Topics such as the Hilbert space, non-closed integration methods, and Fourier analysis have been exclusively covered in my physics courses, for example.
#11
Thanks I was just wondering what kind of classes are out there.

Don't want to be an actor pretending on the stage
Don't want to be a writer with my thoughts out on the page
Don't want to be a painter 'cause everyone comes to look
Don't want to be anything where my life's an open book

Phish - Waste
#12
Quote by Logic Smogic


On that picture q is positive but you've labelled the green line with a -q gradient when the gradient should be positive.
#13
Quote by IrishBlues
Thanks I was just wondering what kind of classes are out there.


No problem. A solid math sequence would go (in my opinion):

Calc 1
Calc 2
Calc 3
Linear Algebra
Ordinary Differential Equations
Topics in Partial Differential Equations or Fourier Analysis
Probability
Real Analysis
Modern Algebra
Complex Analysis
#14
Quote by Gaz_m2k5
On that picture q is positive but you've labelled the green line with a -q gradient when the gradient should be positive.


Good point, I'll change it.



EDIT: Done.
Last edited by Logic Smogic at Jan 17, 2007,
#16
that's already in terms of W, if you wanted W in terms of T then:

W = (T/40) - 20 i believe
Quote by Felkara
Dude, you just made the most intelligent post in this entire thread. Congrats.
#19
Quote by The Postman
Make V the subject of the formula m(v-u)=I



m(v-u) = I

mv - mu = I

mv = I + mu

v = (I + mu)/m

i think.