What's the difference between てform+行くand てform+いる?


I know what both mean and are used for, but when I look at my reference
materials, the former is often used to express the same thing as the latter.
Are details to this that I'm not getting?




_I will assume by 「ていく」 you do not mean "Do something and leave"._

When you are 「ている」, you are doing it now. No reference to the future.

When you will 「ていく」, you will do it from now, from this point on.

So,

>   1. 「ていく」implies continued effort, where as 「ている」 is only about what you
> are doing now.
>
>   2. 「ていく」doesn't necessarily imply that you weren't doing it before. It
> depends on the context. (i.e.「これからも引き続き工場の安全を確保するために全力を尽くし **て行き**
> たいと思っております。」= "We will continue to work hard to maintain safety at our
> factories.")
>
>




_I will assume by 「ていく」 you do not mean "Do something and leave"._

When you are 「ている」, you are doing it now. No reference to the future.

When you will 「ていく」, you will do it from now, from this point on.

So,

>   1. 「ていく」implies continued effort, where as 「ている」 is only about what you
> are doing now.
>
>   2. 「ていく」doesn't necessarily imply that you weren't doing it before. It
> depends on the context. (i.e.「これからも引き続き工場の安全を確保するために全力を尽くし **て行き**
> たいと思っております。」= "We will continue to work hard to maintain safety at our
> factories.")
>
>

