---
tags : Mechanics,Mathmatics
title : 2020.4.8(8)
---
# Mechanics(8)
## Conclusion of words in chapter 3
### Bector cross product
We write a bector cross product of bector **A, B** as

$\huge A \times B$

This is a bector which has a parallelogram area made of bector **A, B** as

$\huge |A \times B| = |A||B||sin\theta|$

This bector's direction is vertical against the area made of bector **A, B**,
and turning right screw A to B.


Bector cross product between basic unit bectors which parallel to x, y, z axis in cartain coordinate system; $i \equiv (1,0,0) , j \equiv (0,1,0) , k \equiv (0,0,1)$ is

$\huge i \times j =k , j \times k =i , k \times i =j$

$\huge i \times i = 0 , j \times j = 0 , k \times k = 0$