It actually has infinite planes of symmetry rotating around its center here.

它实际上有无限的对称平面围绕着它的中心旋转。

This happens because the mirror is parallel with the plane of symmetry.

这是因为镜子与对称平面平行。

So just like 2D shapes can have a 1D line of symmetry, 3D shapes can have a 2D plane of symmetry.

所以就像二维形状可以有一维对称线，三维形状可以有一个二维对称平面。

But what if we point the cones so that the mirror is now at a right angle to the plane of symmetry?

但是如果我们把锥体指向镜面，使镜面与对称面成直角呢？