Update textbook.fr.md

01.curriculum/01.physics-chemistry-biology/04.Niv4/04.electromagnetism/interferences-diffraction/interference-diffraction-main/textbook.fr.md

@@ -188,7 +188,7 @@ $`\underline{A_{tot}}=A\cdot \dfrac{e^{i\,N\,\phi}-1}{e^{i\,\phi}-1}=\dfrac{(1-c
 
 L'**intensité résultante** est alors
 
-$`I_{tot}=\underline{A_{tot}}\,\underline{A^*_{tot}}=|\underline{A_{tot}}^2|=A_{tot}^2=A^2\cdot\dfrac{(1-cos^2\,N\phi)+sin^2\,N\phi}{(1-cos^2\,\phi)+sin^2\,\phi}`$
+$`I_{tot}=\underline{A_{tot}}\,\underline{A^*_{tot}}=|\underline{A_{tot}}^2|=A_{tot}^2=A^2\cdot\dfrac{(1-cos\,N\phi)^2+sin^2\,N\phi}{(1-cos\,\phi)^2+sin^2\,\phi}`$
 
 $`\quad=A^2\cdot\dfrac{1-2\cos\,N\phi+cos^2\,N\phi+sin^2\,N\phi}{1-2\cos\,\phi+cos^2\,\phi+sin^2\,\phi}= A^2\cdot\dfrac{2-2\cos\,N\phi}{2-2\cos\,\phi}`$