"Know" vs "find out"
I'm wondering if it's also okay to use "know" instead of "find out" in this situation?

1. If he knows that you're pregnant, he must be happy.
2. If he finds out that you're pregnant, he must be happy.

For me, I feel "find out" mean the person does something in order to know something, for example, asking around. But "know" means they don't put in any effort, they just know it, maybe someone tells him. There are differences.

Am I right?

Thank you.

Question

"Know" vs "find out"
I'm wondering if it's also okay to use "know" instead of "find out" in this situation?

1. If he knows that you're pregnant, he must be happy. 
2. If he finds out that you're pregnant, he must be happy.

For me, I feel "find out" mean the person does something in order to know something, for example, asking around. But "know" means they don't put in any effort, they just know it, maybe someone tells him. There are differences.

Am I right?

Thank you.

Answer

"find out" - to learn new information (non educational), it implies you did not know beforehand. 
It is a colloquial synonym for "discover"

Example:
"I will find out her name" - I don't know her name but I will in the future.
"I found out I love crab" - I did not know I loved crab but I learned after that I did"

"Do you know who the criminal is?"

person 1: "I know" (I know)
person 2: "I am finding out" (I don't know but am learning/discovering)

Answer

Hello.

No, that is not correct.  “To find out” is something you just learned and can be accidental.  For example, I was talking to my neighbor and I just found out that she’s pregnant (she just told me while we were talking but I was not necessarily actively seeking out this information).

Answer

So in my opinion, both are right but at the end of  "If he finds out that you're pregnant, he must be happy."

You would change "he must be happy" To "he will be happy."  the time in this case is why you would change it. If he already knows. Then he must be happy, but if he hasn't already found out, then he will be happy. hope this helps.