Left implication

[visual whale]

Here, why is left implication necessary?

[rich chasm]

1. Ask your question and show the work you've done so far. If you've posted a screenshot of a question, specify which part you need help with.
2. Wait patiently for a helper to come along.
3. Once someone helps you, say thank you and close the thread with:

   +close
   

4. Feel free to nominate the person for helper of the week in #helper-nominations
5. Do not ping the mods, unless someone is breaking the rules.
6. If you're happy with the help you got here, and the server overall, you can contribute financially as well:

[visual whale]

Why did they not use <=>

[unreal summit]

either because it isn't true or don't need it for the argument

first implication works both ways

and the second one also

probably they don't need the other direction, then

@visual whale

[visual whale]

Oh, thanks

[leaden sinew]

@visual whale has given 1 rep to @unreal summit

[visual whale]

+close