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Derivative of a product involving e^(2x) and arcsin(x)

Consider the function y=e2xarcsin⁡(x)y = e^{2x} \arcsin(x).

Find dydx\dfrac{dy}{dx} for y=e2xarcsin⁡(x)y = e^{2x}\arcsin(x), and then evaluate dydx\dfrac{dy}{dx} at x=0x = 0.

Hint

Use the product rule with f(x)=e2xf(x) = e^{2x} and g(x)=arcsin⁡(x)g(x) = \arcsin(x). Remember that ddx[e2x]=2e2x\frac{d}{dx}[e^{2x}] = 2e^{2x} by the chain rule, and ddx[arcsin⁡(x)]=11−x2\frac{d}{dx}[\arcsin(x)] = \frac{1}{\sqrt{1-x^2}}.

Step-by-step solution

Apply the product rule: dydx=ddx[e2x]⋅arcsin⁡(x)+e2x⋅ddx[arcsin⁡(x)]\frac{dy}{dx} = \frac{d}{dx}[e^{2x}] \cdot \arcsin(x) + e^{2x} \cdot \frac{d}{dx}[\arcsin(x)]. Since ddx[e2x]=2e2x\frac{d}{dx}[e^{2x}] = 2e^{2x} (chain rule) and ddx[arcsin⁡(x)]=11−x2\frac{d}{dx}[\arcsin(x)] = \frac{1}{\sqrt{1-x^2}}, this gives dydx=2e2xarcsin⁡(x)+e2x1−x2\frac{dy}{dx} = 2e^{2x}\arcsin(x) + \dfrac{e^{2x}}{\sqrt{1-x^2}}.

Now substitute x=0x = 0: arcsin⁡(0)=0\arcsin(0) = 0, e0=1e^{0} = 1, and 1−02=1\sqrt{1-0^2} = 1. So dydx∣x=0=2(1)(0)+11=1\frac{dy}{dx}\Big|_{x=0} = 2(1)(0) + \dfrac{1}{1} = 1.

Value of arcsine term at x equals zero

Hint
Step-by-step solution

Arcsine of zero equals zero, so the term two times e to the zero times arcsine of zero vanished completely. This means that entire product contributed zero to the final answer at x equals zero. The only surviving term was e to the zero divided by the square root of one, which equals one. So arcsine of zero contributed nothing, that is, zero.

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