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Applied Mathematics · Ch 3 — Differentiation and Its Applications

Recall Some Standard Results of Differentiation

3.2

Recall Some Standard Results of Differentiation

Before working through this chapter, it helps to recall the standard derivatives and differentiation rules you've already met in Class XI. For a power function, ddx(xn)=nxn−1\dfrac{d}{dx}(x^n) = nx^{n-1}; for an exponential function, ddx(ax)=axlog⁡a\dfrac{d}{dx}(a^x) = a^x \log a and, as a special case, ddx(ex)=ex\dfrac{d}{dx}(e^x) = e^x; and for the natural logarithm, ddx(log⁡x)=1x\dfrac{d}{dx}(\log x) = \dfrac{1}{x}. The derivative of any constant is zero.

Alongside these, four basic rules let you differentiate combinations of functions:

ddx[k f(x)]=k ddxf(x)\dfrac{d}{dx}[k\,f(x)] = k\,\dfrac{d}{dx}f(x), where kk is a real number

ddx[f(x)±g(x)]=ddxf(x)±ddxg(x)\dfrac{d}{dx}[f(x) \pm g(x)] = \dfrac{d}{dx}f(x) \pm \dfrac{d}{dx}g(x)

ddx[f(x) g(x)]=f(x)ddxg(x)+g(x)ddxf(x)\dfrac{d}{dx}[f(x)\,g(x)] = f(x)\dfrac{d}{dx}g(x) + g(x)\dfrac{d}{dx}f(x) — the product rule

ddx ⁣[f(x)g(x)]=g(x)ddxf(x)−f(x)ddxg(x)[g(x)]2\dfrac{d}{dx}\!\left[\dfrac{f(x)}{g(x)}\right] = \dfrac{g(x)\frac{d}{dx}f(x) - f(x)\frac{d}{dx}g(x)}{[g(x)]^2} — the quotient rule …