Vector a=(x 1, y 1), vector b=(x2, y2), x 1y2-x2y 1=0. The necessary and sufficient condition for a⊥b is that a b = 0, that is, (x 1x2+y 1y2)=0.

"In mathematics, vectors (also known as Euclidean vectors, geometric vectors, vectors) refer to quantities with size and direction. ... if a=(x, y) and b=(m, n), then a//b→a×b=xn-ym=0 ".

Parallel vector: A nonzero vector with the same or opposite direction is called a parallel (or * * * line) vector. The parallel (* * * line) of vectors A and B is marked as A∨B, and the length of zero vector is zero, which is a vector whose starting point and ending point coincide, and the direction is uncertain. We stipulate that the zero vector is parallel to any vector. A set of vectors parallel to the same line is a * * * line vector.

If a=(x, y) and b=(m, n), then a//b→a×b=xn-ym=0.

* * * line theorem: If b≠0, then a/b is necessary and sufficient if there is a unique real number λ, so that vector a=λ vector B. If a=(x 1, y 1) and b=(x2, y2), then there is x/kloc-0. The 0 vector is parallel to any vector.