Knowing or having known
When writing a letter, I have a dilemma about using “ knowing that you are conducting a research, I am writing to give you some related information.” or “having known that you are conducting a research, I am writing to give you some related information.” Which one is correct? Thank you in advance.

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Hi Yun, the first option is best in this case as the tenses match — "knowing" and "writing" — verses the passive past tense of the second option.

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The first one is the best.

To put it in simple English,
"having known" is used when you are talking about something in the past. For example, "YESTERDAY, having known that she would be here at 6:00 AM, I left the house a bit earlier."

"knowing X, Y" means "at this time I know that X is the case, therefore Y"

I hope that helps ^_^

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(Responded in the wrong area.)