Update textbook.en.md

6 years ago · ba67d28f08
1 changed files with 3 additions and 1 deletions
--- a/light/01.electromagnetic-spectrum/01.new-course-main/textbook.en.md
+++ b/light/01.electromagnetic-spectrum/01.new-course-main/textbook.en.md
@ -5,3 +5,5 @@ published: no

 test :
 $`\oiint_S \vec{B} \cdot \vec{dS}`$
+
+$`\Longoiint_S \vec{B} \cdot \vec{dS}`$