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pac.tex
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pac.tex
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\documentclass{article}
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\usepackage{amsmath}
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\usepackage{geometry}
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\usepackage[colorlinks=true, linkcolor=blue, urlcolor=blue]{hyperref}
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\usepackage{enumitem}
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\geometry{a4paper, margin=1in}
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\begin{document}
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\Large
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\section{Preuves A Connaitre (PAC)}
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\subsection{Chapitre 1}
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\subsubsection{Les identités structurales usuelles.}
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\begin{itemize}
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\item
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Soit $Z_1 et Z_2$ des nombres complexes, alors on a les égalités:
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\[
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\overline{Z_1 + Z_2} = \overline{Z_1} + \overline{Z_2}
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\]
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\[
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\overline{Z_1 \times Z_2} = \overline{Z_1} \times \overline{Z_2}
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\]
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\[
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\lvert Z_1 \times Z_2\rvert = \lvert Z_1 \rvert \times \lvert Z_2 \rvert
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\]
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\item Demonstrations:
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\[
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Z_1 = a+ib \]
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\[Z_2 = a^\prime +ib^\prime\]
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\begin{itemize}
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\item $\overline{Z_1 + Z_2} = \overline{Z_1} + \overline{Z_2}:$
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\[
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\overline{Z_1 + Z_2} = \overline{a + ib + a^\prime + ib^\prime} = a + a ^\prime - i\left(b + b^\prime\right)
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\]
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or
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\[
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\overline{Z_1} + \overline{Z_2} = \overline{a+ib} + \overline{a^\prime+ib^\prime} = a + a ^\prime - i\left(b + b^\prime\right)
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\]
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donc:
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\[\overline{Z_1 + Z_2} = \overline{Z_1} + \overline{Z_2} \]
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\item $\overline{Z_1 Z_2} = \overline{Z_1}\,\overline{Z_2}:$
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\[
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Z_1Z_2=(a+ib)(a'+ib')=aa'-bb' + i(ab'+a'b)
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\]
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\[
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\overline{Z_1Z_2}=aa'-bb' - i(ab'+a'b)
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\]
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or
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\[
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\overline{Z_1}\,\overline{Z_2}=(a-ib)(a'-ib')=aa'-bb' - i(ab'+a'b)
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\]
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donc:
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\[
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\overline{Z_1 Z_2}=\overline{Z_1}\,\overline{Z_2}
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\]
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\item $\lvert Z_1Z_2\rvert=\lvert Z_1\rvert\,\lvert Z_2\rvert:$
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\[
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Z_1=a+ib,\qquad Z_2=a'+ib'
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\]
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\[
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Z_1Z_2=(a+ib)(a'+ib')=aa'-bb' + i(ab'+a'b)
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\]
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\[
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\lvert Z_1Z_2\rvert^2=(aa'-bb')^2+(ab'+a'b)^2
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\]
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\item
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Développer séparément :
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\[
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\lvert Z_1\rvert^2=a^2+b^2,\qquad \lvert Z_2\rvert^2=a'^2+b'^2
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\]
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Produit :
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\[
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\lvert Z_1\rvert^2\,\lvert Z_2\rvert^2=(a^2+b^2)(a'^2+b'^2)
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\]
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Égalité d’identité algébrique :
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\[
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(aa'-bb')^2+(ab'+a'b)^2=(a^2+b^2)(a'^2+b'^2)
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\]
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Donc :
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\[
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\lvert Z_1Z_2\rvert^2=\lvert Z_1\rvert^2\,\lvert Z_2\rvert^2
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\]
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\[
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\lvert Z_1Z_2\rvert=\lvert Z_1\rvert\,\lvert Z_2\rvert
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\]
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\end{itemize}
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\end{itemize}
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\subsubsection{Solutions d'un polynôme du second degré}
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\begin{itemize}
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\item Soit $Z_1, Z_2 \in \mathbf{C} $ des solutions d'un polynôme de degré 2 telles que:
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\[
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a\left(z - Z_1\right)\left(z - Z_2\right) = az^2 + bz + c
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\]
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on cherche a vérifier que $Z_1$ et $Z_2$ sont solutions de $az^2 + bz + c$
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\item Demonstration:
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\[
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Z_1 = \frac{-b+\delta}{2a}
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\]
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\[
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Z_2 = \frac{-b-\delta}{2a}
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\]
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Avec $\delta^2 = \Delta$ et $\Delta = b^2 - 4ac$ \\
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On obtient donc avec le membre de gauche:
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\[
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a\left(z-Z_1\right)\left(z-Z_2\right) = a\left(z - \frac{-b+\delta}{2a}\right)\left(z - \frac{-b-\delta}{2a}\right)
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\]
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\[
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=a\left(z^2 -z \times\left(\frac{-b-\delta}{2a} + \frac{-b+\delta}{2a}\right) + \frac{b^2 - \delta^2}{4a^2}\right)
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\] or $\delta^2 = \Delta = b^2 - 4ac$
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\[
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=a\left(z^2+z\frac{b}{a}+\frac{-b^2-b^2+4ac}{4a^2}\right)
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= \boxed{az^2 + bz + c}
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\]
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Qui correspond au membre de droite donc à une equation de degré 2.
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\end{itemize}
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\end{document}
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