Differentiate the following w.r.t. xx : (i) e−xe^{-x} (ii) sin⁡(log⁡x),x>0\sin (\log x), x>0 (iii) cos⁡−1(ex)\cos ^{-1}\left(e^{x}\right) (iv) ecos⁡xe^{\cos x}

Answer: (i) −e−x-e^{-x} (ii) cos⁡(log⁡x)x\frac{\cos (\log x)}{x} (iii) −ex1−e2x\frac{-e^x}{\sqrt{1 - e^{2x}}} (iv) −sin⁡x⋅ecos⁡x-\sin x \cdot e^{\cos x}

Step-by-step solution

Step 1: Differentiate e−xe^{-x}

To differentiate e−xe^{-x}, we use the chain rule. The derivative of eue^u with respect to xx is eu⋅dudxe^u \cdot \frac{du}{dx}. Here, u=−xu = -x. We differentiate e−xe^{-x} with respect to −x-x, and then multiply by the derivative of −x-x with respect to xx.

Step 2: Simplify the derivative of e−xe^{-x}

The derivative of −x-x with respect to xx is −1-1. Multiplying e−xe^{-x} by −1-1 gives us the final derivative.

Step 3: Differentiate sin⁡(log⁡x)\sin (\log x)

For sin⁡(log⁡x)\sin (\log x), we again use the chain rule. The derivative of sin⁡u\sin u is cos⁡u⋅dudx\cos u \cdot \frac{du}{dx}. Here, u=log⁡xu = \log x. We differentiate sin⁡(log⁡x)\sin (\log x) with respect to log⁡x\log x, and then multiply by the derivative of log⁡x\log x with respect to xx.

Step 4: Simplify the derivative of sin⁡(log⁡x)\sin (\log x)

The derivative of log⁡x\log x with respect to xx is 1x\frac{1}{x}. Multiplying cos⁡(log⁡x)\cos (\log x) by 1x\frac{1}{x} gives the final derivative.

Step 5: Differentiate cos⁡−1(ex)\cos^{-1}(e^x)

We use the chain rule for cos⁡−1(ex)\cos^{-1}(e^x). The derivative of cos⁡−1u\cos^{-1} u is −11−u2⋅dudx\frac{-1}{\sqrt{1 - u^2}} \cdot \frac{du}{dx}. Here, u=exu = e^x. We differentiate cos⁡−1(ex)\cos^{-1}(e^x) with respect to exe^x, and then multiply by the derivative of exe^x with respect to xx.

Step 6: Simplify the derivative of cos⁡−1(ex)\cos^{-1}(e^x)

The derivative of exe^x with respect to xx is exe^x. Substituting this and simplifying gives the final derivative.

Step 7: Differentiate ecos⁡xe^{\cos x}

For ecos⁡xe^{\cos x}, we use the chain rule. The derivative of eue^u is eu⋅dudxe^u \cdot \frac{du}{dx}. Here, u=cos⁡xu = \cos x. We differentiate ecos⁡xe^{\cos x} with respect to cos⁡x\cos x, and then multiply by the derivative of cos⁡x\cos x with respect to xx.

Step 8: Simplify the derivative of ecos⁡xe^{\cos x}

The derivative of cos⁡x\cos x with respect to xx is −sin⁡x-\sin x. Multiplying ecos⁡xe^{\cos x} by −sin⁡x-\sin x gives the final derivative.

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