⊥ is a mathematical symbol which means vertical. Perpendicular means that one line is at right angles to the other, and these two straight lines are perpendicular to each other. The symbol "⊥". "is usually used to indicate that there are two vectors A and B. a⊥b is necessary and sufficient if a b = 0, that is, (x 1x2+y 1y2)=0.

For the vertical problem in solid geometry, it mainly involves the vertical problem of straight line and plane and the vertical problem of plane. To solve related problems, the difficulty lies in the definition of straight line perpendicular to plane and its understanding of theorem judgment conditions. Judgement theorem of two planes perpendicular and its application and understanding of some concepts of dihedral angle.