1基向量--
长度为一个单位长度的向量
Every vector a in three dimensions is a linear combination of the standard basis vectors i, j, and k.
2向量叉积--
方向根据右手法则确定，就是手掌立在a、b所在平面的向量a上，掌心由a转向b的过程中，大拇指的方向就是叉积的方向。
The cross product is defined by the formula
推到公式：
The standard basis vectors i, j, and k satisfy the following equalities in a right hand coordinate system。
角度大于90 ===》 
角度为0===》
meaning that the three scalar components of the resulting vector s = s1i + s2j + s3k = u × v are
Using column vectors, we can represent the same result as follows:
The cross product can also be expressed as the formal[note 1] determinant:
