A calculus problem by Rajdeep Dhingra

Calculus Level 1

Question in image


The answer is 1.

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3 solutions

Rajdeep Dhingra
Feb 18, 2014

l e t f ( x ) = y s o f ( x ) = x y y = x y t a k e l o g b o t h s i d e l o g y = y l o g x n o w d i f f e r c i a t i n g b o t h s i d e s w e g e t 1 y d y d x = y x + d y d x ( l o g x ) o n s o l v i n g d y d x = y x [ 1 y l o g x ] p u t t i n g x = 1 ( y w i l l a l s o b e 1 ) w e g e t d d x [ f ( x ) ] = 1 let\quad f\left( x \right) =y\\ so\quad f\left( x \right) =\quad { x }^{ y }\\ \quad \quad \quad y={ x }^{ y }\\ take\quad log\quad both\quad side\\ log\quad y\quad =\quad y*log\quad x\\ now\quad differciating\quad both\quad sides\quad we\quad get\\ \frac { 1 }{ y } \frac { dy }{ dx } \quad =\quad \frac { y }{ x } +\quad \frac { dy }{ dx } (log\quad x)\\ on\quad solving\quad \\ \frac { dy }{ dx } =\quad \frac { y }{ x[\frac { 1 }{ y } -\quad log\quad x] } \\ putting\quad x=1\quad (\quad y\quad will\quad also\quad be\quad 1\quad )\quad we\quad get\\ \frac { d }{ dx } [f\left( x \right)]=\quad 1

what if it is x^x^x ????

Parth Lohomi - 6 years, 11 months ago

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then just take y= x^x^x take log and differenciate

Rajdeep Dhingra - 6 years, 8 months ago

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Panshul Rastogi - 6 years, 9 months ago

f'(x)=x(x^x^x^x^(x-1)=x[f(x)] f'(1)=(1)[f(1)] = 1

Hemu Singh
Feb 18, 2014

Let f(x) = y =x^y Taking log

ln(y) = y ln(x)

Y'=y^2/[x{1-ln(y)]

x=1,y=1 Putting we get

Y'=1

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