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fimd-lim-x-0-sinx-x-1-x-1-x-x-2-




Question Number 29458 by prof Abdo imad last updated on 08/Feb/18
fimd lim_(x→0)     ((((sinx)/(x(1+x)))−1+x)/x^2 ) .
$${fimd}\:{lim}_{{x}\rightarrow\mathrm{0}} \:\:\:\:\frac{\frac{{sinx}}{{x}\left(\mathrm{1}+{x}\right)}−\mathrm{1}+{x}}{{x}^{\mathrm{2}} }\:. \\ $$
Commented by prof Abdo imad last updated on 13/Feb/18
=lim_(x→0)      ((sinx +x(x−1)(x+1))/(x^3 (1+x)))  =lim_(x→0)    ((sinx +x(x^2 −1))/(x^3 (1+x)))  =lim_(x→0)      ((sinx +x^3 −x)/(x^3 (1+x))) but  for x∈V(0)  sinx∼x ⇒  ((sinx +x^3 −x)/(x^3 (1+x)))∼ (1/(1+x))  ⇒ lim(...)=1 .
$$={lim}_{{x}\rightarrow\mathrm{0}} \:\:\:\:\:\frac{{sinx}\:+{x}\left({x}−\mathrm{1}\right)\left({x}+\mathrm{1}\right)}{{x}^{\mathrm{3}} \left(\mathrm{1}+{x}\right)} \\ $$$$={lim}_{{x}\rightarrow\mathrm{0}} \:\:\:\frac{{sinx}\:+{x}\left({x}^{\mathrm{2}} −\mathrm{1}\right)}{{x}^{\mathrm{3}} \left(\mathrm{1}+{x}\right)} \\ $$$$={lim}_{{x}\rightarrow\mathrm{0}} \:\:\:\:\:\frac{{sinx}\:+{x}^{\mathrm{3}} −{x}}{{x}^{\mathrm{3}} \left(\mathrm{1}+{x}\right)}\:{but}\:\:{for}\:{x}\in{V}\left(\mathrm{0}\right) \\ $$$${sinx}\sim{x}\:\Rightarrow\:\:\frac{{sinx}\:+{x}^{\mathrm{3}} −{x}}{{x}^{\mathrm{3}} \left(\mathrm{1}+{x}\right)}\sim\:\frac{\mathrm{1}}{\mathrm{1}+{x}} \\ $$$$\Rightarrow\:{lim}\left(…\right)=\mathrm{1}\:. \\ $$

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