No. In this type of language, the typical division function does not check against zero. It has a precondition that requires the caller to ensure that the divisor is not zero. If the data the caller has is completely arbitrary, then yes, the caller must use an if statement or similar. If the caller knows something about its data and can be sure that the divisor is not zero, then it doesn't need to use an if statement. But it might need to convince the proof checker that it knows what it's doing.
This is a very antagonistic comment. Some people would call it "passive aggressive".
Dude, if you're reading to your kid you're clearly busy doing something else. No matter how simple the concept is, if you don't pay attention you're not going to get it so it's a failure on your part and not a failure on the part of the person patiently trying to explain something to you.