ST259 Lecture Notes - If And Only If
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4lDeterminantsoforderI
DefI
Aqbd is a22matrix withentriesfrom afield Fthen we define the
determinant of Adenoted det Aor lat tobethescalar adibc
Tha4.1
Thefunction Det Marz FFis alinearfunction of each row of a22matrix
whentheother row is heldfixedThat is if urand ware in FZand Kis ascalar
then
detfutwk detgkdetfw
and
det www detfwu tkdetfw
ThM4.2 Let A
EM
22FThenthedeterminant of Ais nonzero iff Ais invertible Moreover
if Ais invertible then
AdefeatHa Aa
The Area of aParrellelogram
Bythe angle betweentwovectors in 1132 we mean the angle with measure 0CO
EOEt
that is formedbythevectors havingthe same magnitude and direction as thegiven
vectors but emanatingfromthe origin
If DuVis an ordered basis for 1132 we define theorientation of Bto be the
real number
det
Idet I
Clearly
ti
Noticethat
0el Iand Ofer I