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If y=log⁡e(sec⁡ex2)y = \log_e(\sec e^{x^2}) then dydx=\frac{dy}{dx} =

Solution

✅ Correct Option: 2

Given: y=log⁡e(sec⁡ex2)y = \log_e(\sec e^{x^2})

Since log⁡e=ln⁡\log_e = \ln and sec⁡θ=1cos⁡θ\sec \theta = \frac{1}{\cos \theta}:

y=ln⁡(1cos⁡ex2)y = \ln\left(\frac{1}{\cos e^{x^2}}\right)

Using the property ln⁡(1a)=−ln⁡(a)\ln\left(\frac{1}{a}\right) = -\ln(a):

y=−ln⁡(cos⁡ex2)y = -\ln(\cos e^{x^2})


Differentiating with respect to xx, where u=cos⁡ex2u = \cos e^{x^2}:

dydx=−1cos⁡ex2⋅ddx(cos⁡ex2)\frac{dy}{dx} = -\frac{1}{\cos e^{x^2}} \cdot \frac{d}{dx}(\cos e^{x^2})


For ddx(cos⁡ex2)\frac{d}{dx}(\cos e^{x^2}), let v=ex2v = e^{x^2}:

ddx(cos⁡ex2)=−sin⁡ex2⋅ddx(ex2)\frac{d}{dx}(\cos e^{x^2}) = -\sin e^{x^2} \cdot \frac{d}{dx}(e^{x^2})


For ddx(ex2)\frac{d}{dx}(e^{x^2}), let w=x2w = x^2:

ddx(ex2)=ex2⋅2x\frac{d}{dx}(e^{x^2}) = e^{x^2} \cdot 2x

ddx(ex2)=2xex2\frac{d}{dx}(e^{x^2}) = 2xe^{x^2}


Combining the results:

ddx(cos⁡ex2)=−sin⁡ex2⋅2xex2\frac{d}{dx}(\cos e^{x^2}) = -\sin e^{x^2} \cdot 2xe^{x^2}

dydx=−1cos⁡ex2⋅(−sin⁡ex2⋅2xex2)\frac{dy}{dx} = -\frac{1}{\cos e^{x^2}} \cdot (-\sin e^{x^2} \cdot 2xe^{x^2})

dydx=sin⁡ex2cos⁡ex2⋅2xex2\frac{dy}{dx} = \frac{\sin e^{x^2}}{\cos e^{x^2}} \cdot 2xe^{x^2}

Using sin⁡θcos⁡θ=tan⁡θ\frac{\sin \theta}{\cos \theta} = \tan \theta:

dydx=2xex2tan⁡ex2\frac{dy}{dx} = 2xe^{x^2} \tan e^{x^2}

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