Question

Which is a real world example of two planes intersecting?

Answer 1

One example is the idea of two parts of a book that open up. Each flat part is a plane and the two planes intersect along the spine of the book.

Another example would be a wall intersecting with the floor. Both are flat surfaces.

A third example would be a laptop's screen as one plane and the keyboard as the other plane. They intersect at the hinge of the laptop.

For each example, the surface has a finite amount of area and it doesn't extend forever in all four directions. Theoretically, a plane is where the flat surface extends in all four directions infinitely. Though of course, real life has limitations but the idea is still applicable in a way.

Note how for each example, the two planes intersect to form a line. Also, each plane must be flat without bending or curving in any way.