Update textbook.fr.md

12.temporary_ins/96.electromagnetism-in-media/20.reflexion-refraction-at-interfaces/20.metallic-waveguides/10.main/textbook.fr.md

@@ -114,21 +114,18 @@ simplicity only the case of TE modes.
 ![](rectangular_waveguide_with_a_TE_mode.jpg)   
 _Rectangular waveguide with a TE mode._
 
-@@@@@@@@@@@@@@@@@@@
-
-![](media/image206.png)
+<br>
 
-Figure 4.2: Rectangular waveguide with a TE mode.
+#### TE modes
 
-chap2 TE modes
 
-chap4 Mode numbering
+##### Mode numbering
 
 In the previous example, we have chose the orientation of the frame to
 describe the rectangular waveguide such that the successive reflection
 of the electric field intervene between the conducting plates placed
-at *y* = 0 and *y* = *b* where *b* = *[nλ]{.underline}* . We will
-describe this wave as a TE~0*,n*~ which signifies that the reflection
+at $`y=0`$ and $`y=b`$ where $`b=\dfrac{n\lambda}{2\,\cos\theta}`$.
+We will describe this wave as a TE~0*,n*~ which signifies that the reflection
 occurs between the plates placed at *y* = 0 and *y* = *b* and that
 >
 ![](media/image212.png) ![](media/image213.png)