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Algebra

Scorching goIITian

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1 Feb 2008 12:31:42 IST

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450

another on functions

Engineering Entrance , JEE Main , JEE Main & Advanced , Mathematics , Algebra

f(x)=(2x- )^3 +2x-cosx. the value of d/dx f inverse of x,x=

Comments (6)

saurabh panda

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1 Feb 2008 12:42:44 IST

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is the ans. 1/2

if yes then i will give the sol...

rockey

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1 Feb 2008 13:12:59 IST

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the ans is 1/3. & i got it too

Rahul Raghavendra

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1 Feb 2008 13:14:44 IST

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could u post the solution

saurabh panda

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1 Feb 2008 16:00:32 IST

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look i am sending u a trick

plz. rate me for it......

when u want to get some inverse, then just exchange the places of x and y. u can know it if u apply pure logic. remember: (f inv.) is reflection of f on line y=x

like here-

x=(2y-pie⁾³+2y- cosy ............... A y =f(x)

this is the inv. of given fn.

now see for x=pie we get y=pie/2 as one ans.

so differentiate A....

and put y=pie/2 as x=pie

putting values we can get ans.

if any prob. nudge me!! or else...

PLZ. RATE ME IF U LIKE IT. i request it to all of u....

saurabh panda

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1 Feb 2008 17:12:35 IST

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hey the ans is 1/2

and i am sure

Nadeem

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1 Feb 2008 17:35:06 IST

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This can be taken as a result d[ f^-1(x)]/dx = reciprocal of d[f(x)] / dx

Here d[f(x)]/dx at x=pi/2 is 3.

So d[ f^-1(x)]/dx = 1/3.

@saurabh : I think u'll get 1/3 with ur method also. just check ur working

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