I used "search" by typing "tex" but only find a thread, it seems to said that by using [tex]...[/tex] , you can type formula well.

So I tried this and preview the post, but it was not valid, and I was confused.

I just typed like below,thx:

[tex]

\nabla(\bf{x}\cdot

\bf{a})=\bf{a}+\bf{x}(\nabla\cdot\bf{a})+i(\bf{L}\times\bf{a})

\ \

where \ \ \bf{L}={\frac{1}{i}}(\bf{x}\times\nabla)

[/tex]

So I tried this and preview the post, but it was not valid, and I was confused.

I just typed like below,thx:

[tex]

\nabla(\bf{x}\cdot

\bf{a})=\bf{a}+\bf{x}(\nabla\cdot\bf{a})+i(\bf{L}\times\bf{a})

\ \

where \ \ \bf{L}={\frac{1}{i}}(\bf{x}\times\nabla)

[/tex]

Last edited: