Author Topic: c4 easy 2 doubts  (Read 1091 times)

Offline zabady

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c4 easy 2 doubts
« on: April 15, 2010, 01:34:42 am »
i have this doubt in the proof of a^x=INa

i kno that y=a^x
log both sides =

INy=xINa

differentiation of iny is easy but when it comes to differentian of xINa i do it by product rule which is X(1/a)+INa

in the book the ignored the x(1/a) thats where i dnt understand i attached the explanation of the book

my second doubt is attached too
« Last Edit: April 15, 2010, 01:36:37 am by zabady »

Offline astarmathsandphysics

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Re: c4 easy 2 doubts
« Reply #1 on: April 15, 2010, 07:53:47 am »
Xlna is not a product. Lna is a constant

Offline zabady

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Re: c4 easy 2 doubts
« Reply #2 on: April 15, 2010, 11:19:35 am »
aha so a constant we would take it as a zero when we differentiate it i have still 1 doubt which is the second picture

Offline T.Q

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Re: c4 easy 2 doubts
« Reply #3 on: April 15, 2010, 11:42:48 am »
FOR the first doubt , u dont have to know how to derive it
just memories it  like a^x =   dy/dx=a^xlna


and for the second doubt, u differentiate the whole equ.

2x+8y(dy/dx)-6-16(dy/dx)=0

make dy/dx subject of the formula

dy/dx=(6-2x)/(8y-16)

dy/dx=0

so , x=3

now substitute the x value in the original equ and solve

y= 1  or 3


so the coordinates are (3,1) , (3,3)
« Last Edit: April 15, 2010, 12:35:30 pm by T.Q »
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Offline zabady

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Re: c4 easy 2 doubts
« Reply #4 on: April 15, 2010, 01:14:09 pm »
ooooh dam i kno that one i gave the wrong question look at the one i attached here i tried solving it same way as the one u just solved but it gives t=1 and in question they say t is not equal to one so how to solve it  ???

Offline T.Q

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Re: c4 easy 2 doubts
« Reply #5 on: April 15, 2010, 01:27:45 pm »
ooooh dam i kno that one i gave the wrong question look at the one i attached here i tried solving it same way as the one u just solved but it gives t=1 and in question they say t is not equal to one so how to solve it  ???

okay


dx/dt= 1/(1-t)^2    &    dy/dt= t(2-t)/(1-t)^2

so divide dy/dt by dx/dt  to give u dy/dx

so , dy/dx= t(2-t)

t= 0 or 2


so the coordinates are

(0,0)  ,   (-2,-4)
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Offline zabady

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Re: c4 easy 2 doubts
« Reply #6 on: April 15, 2010, 01:43:51 pm »
thaaankz so much man sry for wastin ur time it waz easy thankz again mannn  ;D  ;D  ;D  ;D  ;D  ;D  ;D  ;D  ;D

Offline T.Q

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Re: c4 easy 2 doubts
« Reply #7 on: April 15, 2010, 01:56:06 pm »
no problem   ;)

im here to help  :)
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Re: c4 easy 2 doubts
« Reply #8 on: April 15, 2010, 02:28:11 pm »
thanks T.Q

+rep

Offline T.Q

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Re: c4 easy 2 doubts
« Reply #9 on: April 15, 2010, 02:49:49 pm »
thanx ~ A.F ~
No Matter What Happens In Life , Just Don't Lose Hope :)