Update textbook.en.md

12.temporary_ins/05.coordinates-systems/30.cylindrical-coordinates/10.main/textbook.en.md

@@ -90,7 +90,7 @@ between point $`O`$ and point $`m_{xy}`$. <br>
 \- The coordinate $`\varphi_M`$ of the point $`M`$ is the nonalgebraic angle
 $`\widehat{xOm_{xy}}`$ between the axis $`Ox`$ and the half-line $`Om_ {xy}`$,
 the direction of rotation being such that the trihedron $`(Ox,Om_{xy},Oz)`$ is a direct trihedron. <br>
-\- The $`z_M`$ coordinate of the point $`M` $ is the algebraic distance $`\overline{Om_z}`$ 
+\- The $`z_M`$ coordinate of the point $`M`$ is the algebraic distance $`\overline{Om_z}`$ 
 between the point $`O`$ and the point $`m_z`$.
 
 A same point $`M`$ located in $`z_M`$ on the axis $`Oz`$ can be represented by any triplet