How many planes of symmetry does this solid have?
Planes of symmetry is a plane that divides the solid into two congruent halves. Here’s an example. If we sliced this solid at the blue plane, our solid, sliced at the blue plane, produces two congruent halves. And we need to determine how many planes of symmetry would do that for this shape.
Here’s a second plane of symmetry. This vertical plane gives us two congruent halves.
There is actually one more plane of symmetry in this figure. This one is maybe a little bit harder to see. It’s a diagonal plane. The diagonal plane would create two congruent halves that look like this.
There are three planes of symmetry for our original solid, diagonal, vertical, and horizontal. In total, three planes of symmetry.