# Difference between revisions of "12-240/Classnotes for Thursday September 20"

From Drorbn

(→Complex number) |
(→Complex number) |
||

Line 12: | Line 12: | ||

(a,b)+(c,d)=(a+c,b+d); (a,b)x(c,d)=(ac-bd,ad+bc) | (a,b)+(c,d)=(a+c,b+d); (a,b)x(c,d)=(ac-bd,ad+bc) | ||

+ | |||

+ | i^2=-1 | ||

+ | |||

[[Image:IMG.jpg]] | [[Image:IMG.jpg]] | ||

[[Image:IMG2.jpg]] | [[Image:IMG2.jpg]] | ||

[[Image:IMG3.jpg]] | [[Image:IMG3.jpg]] |

## Revision as of 12:31, 21 September 2012

In this class, the professor completes the lecture about complex number and then introduces vector space.

## Complex number

**Definition:**

** C**={(a,b): a, b **R**}

1 ( of **C**) = (1,0); 0 ( of **C**)= (0,0)

i=(0,1)

(a,b)+(c,d)=(a+c,b+d); (a,b)x(c,d)=(ac-bd,ad+bc)

i^2=-1