Question Details

If x = exp {tan-1(y−x²/x²)}, then dy/dx equals

Options

A

2x [1 + tan (log x)] + x sec² (log x)

B

x [1 + tan (log x)] + sec² (log x)

C

2x [1 + tan (logx)] + x² sec² (log x)

D

2x [1 + tan (log x)] + sec² (log x)

Correct Answer :

2x [1 + tan (log x)] + x sec² (log x)

Solution :

The correct option is: 2x [1 + tan (log x)] + x sec² (log x)

Step-by-step derivation:

We are given the relation:
x = exp { tan 1 ( y x 2 x 2 ) }

Taking the natural logarithm (log) on both sides of the equation:
log x = tan 1 ( y x 2 x 2 )

Taking the tangent (tan) on both sides:
tan ( log x ) = y x 2 x 2

Now, we solve for y by multiplying both sides by x2:
x 2 tan ( log x ) = y x 2
Adding x2 to both sides gives:
y = x 2 + x 2 tan ( log x )
Factoring out x2:
y = x 2 [ 1 + tan ( log x ) ]

Now, we differentiate y with respect to x using the product rule:
d y d x = d d x ( x 2 ) [ 1 + tan ( log x ) ] + x 2 d d x [ 1 + tan ( log x ) ]

Compute the individual derivatives:
1) The derivative of the first term is:
d d x ( x 2 ) = 2 x
2) The derivative of the second term using the chain rule is:
d d x [ 1 + tan ( log x ) ] = sec 2 ( log x ) 1 x

Substituting these derivatives back into the product rule formula:
d y d x = 2 x [ 1 + tan ( log x ) ] + x 2 [ sec 2 ( log x ) 1 x ]
Simplifying the second term by cancelling out x:
d y d x = 2 x [ 1 + tan ( log x ) ] + x sec 2 ( log x )

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