Brenda observes that the keyboard and the screen of an open laptop lie on two different planes. In how many lines do the planes containing the keyboard and the screen intersect?

Question

luffingsails · Answer

Two planes can:

1) never intersect when parallel,
2) intersect across infinite lines when coplanar, and
3) intersect on one line otherwise.

You gave an example of number 3.

anonymous · Answer

so 3?

luffingsails · Answer

Sorry, I meant that the 3rd choice is what you are looking for. 

Two planes, at different angles (they are not parallel), intersect on 1 line.

anonymous · Answer

Thank you!! :)

luffingsails · Answer

No problem.

anonymous · Answer

Can you guys help me out with a problem I have???