Question Details

If y = (tan x)ˢᶦⁿ ˣ, then dy/dx is equal to

Options

A

sec x + cos x

B

sec x+ log tan x

C

(tan x)ˢᶦⁿ ˣ

D

None of these

Correct Answer :

None of these

Solution :

The correct option is "None of these".

To find the derivative of the given function, we use the method of logarithmic differentiation.

Let the given function be:
y = ( tan x ) sin x

Taking the natural logarithm (log to the base e) on both sides:
log y = log [ ( tan x ) sin x ]

Using the logarithmic property log(ab)=bloga, we can rewrite the equation as:
log y = sin x log ( tan x )

Now, differentiating both sides with respect to x:
1 y d y d x = d d x [ sin x log ( tan x ) ]

Applying the product rule of differentiation, ddx[uv]=udvdx+vdudx:
1 y d y d x = sin x d d x [ log ( tan x ) ] + log ( tan x ) d d x ( sin x )

Using the chain rule, the derivative of log(tanx) is 1tanxsec2x:
1 y d y d x = sin x [ 1 tan x sec 2 x ] + log ( tan x ) cos x

Let us simplify the first term:
sin x cos x sin x 1 cos 2 x = 1 cos x = sec x

Substituting this back into our expression:
1 y d y d x = sec x + cos x log ( tan x )

Multiplying both sides by y:
d y d x = y [ sec x + cos x log ( tan x ) ]

Replacing y with its original value (tanx)sinx:
d y d x = ( tan x ) sin x [ sec x + cos x log ( tan x ) ]

Comparing this derivative with the options:
Option 1: secx+cosx (Incorrect)
Option 2: secx+logtanx (Incorrect)
Option 3: (tanx)sinx (Incorrect)

Since the derived expression does not match any of the first three options, the correct answer is "None of these".

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