1. If two straight lines a and B are different, how can the plane passing through a and perpendicular to B not exist? I don't know. How can there be one? 2. The side of a pyramid is a triangle with a common vertex. If the side of a pyramid is an equilateral triangle, how many side triangles does the pyramid have at most? What is a triangle with a common vertex? What does it look like-

1. If two straight lines a and B are different, how can the plane passing through a and perpendicular to B not exist? I don't know. How can there be one? 2. The side of a pyramid is a triangle with a common vertex. If the side of a pyramid is an equilateral triangle, how many side triangles does the pyramid have at most? What is a triangle with a common vertex? What does it look like-

(1) If there is a plane a perpendicular to B, then B is perpendicular to any straight line in the plane, which contradicts a and B, so it does not exist
(2) Just like the pyramid, the point on the head is the common vertex. There are at most five points in this question, because if the side is projected onto the ground, the sum of angles should be no more than 360, which is obviously five