MATHS study thread. (2 Viewers)

[klaw]

what is the diff between number plane and number line again?

 

[insert-username]

Plane is your x and y Cartesian plane. Number line is... a line... with numbers along it.


I_F

 

[.ben]

hey can anyone xplain how to differentiate logs and exponentials for me? i kinda don't understand it. e.g 2^x

thanks

 

[insert-username]

Deriving log functions and exponential functions isn't part of the Prelim course, so you might like to try the Maths forum.


I_F

 

[klaw]

hey can anyone xplain how to differentiate logs and exponentials for me? i kinda don't understand it. e.g 2^x

thanks

You can only differentiate logs if it is to the base e. and then you just put the derivative of the logged bit over the logged bit. For example, y=ln 2x, y'=2/2x=1/x

For differentiating exponentials of e, you times the derivative the index of e by f(x). e.g. f(x)=e^2x
f'(x)=2f(x)
=2e^2x

 

[.ben]

You can only differentiate logs if it is to the base e. and then you just put the derivative of the logged bit over the logged bit. For example, y=ln 2x, y'=2/2x=1/x

For differentiating exponentials of e, you times the derivative of e by f(x). e.g. f(x)=e^2x
f'(x)=2f(x)
=2e^2x

thanks klaw! no i get it!

 

[klaw]

np... work through the examples in your textbook, there'd only be a few... it's good coz they have worked solutions and everything for you to compare your working out to or for you to look at if you're stuck

 

[[Damo]]

hey can anyone xplain how to differentiate logs and exponentials for me? i kinda don't understand it. e.g 2^x

thanks

2^x
let y=2^x
(take log of both sides)
lny=xln2
x=lny/ln2
dx/dy= 1/yln2
(take recipricol)
dy/dx= yln2
(since y=2^x)
therefore: 2^xln2

 

[Riviet]

BUMP!!
Differentiate x²=4ay
i) with respect to x.
ii) with respect to y.

 

[mitsui]

woot! an ancient thread come bak alife!! Oo
except.. wat does ur Q means riviet?

 

[Riviet]

Um... lol, it means to make x or y the subject and then differentiate with respect to it. Great timing for your test tomorrow, mine's on thursday and MX1 is on friday, if you have any more revision questions post them up asap and i'll reply asap ^_^

 

[mitsui]

oh rite. umm.. i think our skool is SLOW
we r onli gonna b testing on locus and parabola, trigonometry
wahaha..
3u and 4u is much later for me. yeay

so far, i found nothin i donno yet for 2u.. [but i always end up flunkin anyway]

 

[insert-username]

Differentiate x²=4ay
i) with respect to x.
ii) with respect to y.

i) x²=4ay

Therefore y = x²/4a

Therefore, assuming a is a constant,

dy/dx = 2x/4a

= x/2a


ii) x²=4ay

Therefore x = √4ay

= 2√(ay)

= 2(ay)^1/2

Assuming a is a constant,

dx/dy = 2(a/2√y)

= a/√y

= a√y/y

How's that?


I_F

 

[.ben]

differentiate x^x

 

[Riviet]

Correct insert-username!!

 

[kido_1]

Alright...

The line y= 71x-315 is a tangent to the curve y=14x^2+17x+13.
Find the point of contact.

 

[Yip]

differentiate x^x

Let y=x^x
logy=logx^x=xlogx
Differentiating both sides with respect to x,
d/dx[logy]=d/dy[logy].dy/dx=1/y.dy/dx=logx+1
dy/dx=ylogx+y=x^x(logx+1)

 

[pLuvia]

y=14x²+17x+13
y'= 28x+17

Tangent m=28

.: y'=28x+17=28
x = 11/28
y = -8039/28

Point of contact (11/28, -8039/28)

 

[kido_1]

oh, ok, thanx.
Find the derivative of x In x.

 

[pLuvia]

y = x lnx
y' = x(1/x) + lnx
= 1 + ln x