Transcription of Lecture 8: Rules for Matrix Math 2270 Operations
1 Math2270-Lecture8 ,itshouldbemostlyareview, ,asitisthefoundationforeverythingelsewe llbedoinginthiscourse!Amatrixisarectangu lararrayofnumbers,andan mbyn Matrix ,alsowrittenrnxn, , :/23\/35\/58(34)+(10Hf\i2)\\23)\\35/12\/ 36313 I=191224)\ ,becauseitisn ,iftwomatriceshavethesamesizeandshape,it ,it ,wecouldnot,forexample, ,however, ,thentheproductABwillbeamatrixwiththenum berofrowsinA, ,forexample, , (AB)3=(rowiofA).(columnjofB).So,asanexam ple,forthematrices)B=(2 TheproductBAdoesnotmakesense,buttheprodu ctABdoes, +B=B+Ac(A+B)=cA+cBA+(B+C)=(A+B)+CC(A+B)= CA+CB(A+B)C=AC+BCA(BC)=(AB)CPerhapsthemo stinteresting,andunexpected,oftheaboveru lesisA(BG)=(AB) ,andthatmatrixmultiplicationisassociativ eisn tobviousfromthedefinitionofhowmatricesar emultiplied,butit , , (12(21N(6521)22)64while(21\(12N(45(65(12 N(2 22)21)65)64)21)221 WeassumethroughoutthatA,B, (A+B)2isdifferentfromA2+2AB+B2,whenandB= (j)IiT/-(c)(o)(d/Io_170(odL3)-()(I/IL-(, f31(A=(Writedownthecorrectrulefor(A+B)(A +B)=A2+ABi9A_+ (30//1(5(L31I3)(3)IC)-3c--/ioc)AM+()(Y// /Yo(oot[7 43 MatrixPowersWecantakepowersofmatrices,bu tonlyifthey ,thenA ,namely=P+and(AP))))))))]
2 = =I, tobetheinverseofA,soA3wouldbeA A A . , ,A3,A4for0200A 0020 00020000o1Oo\oof0zoOQ0Oo00C-)0C)a0A3o0l0 /0oLQJ-00//0 IQoZ(000 Qooc))LA /0LQ(QQ\ o0000oc00000Ac(15cme/2 JjI.