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Bayangan garis 7 x + 4 y = 9 oleh rotasi ( 0 , 22 5 ∘ ) adalah ax + by = − 9 2 ​ maka nilai a + b = ….

Bayangan garis  oleh rotasi  adalah  maka nilai a + b = ….space space 

  1. 8

  2. 12

  3. 14

  4. -12

  5. -8

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Jawaban

 begin mathsize 14px style a and b equals 3 plus 11 equals 14. end style undefined   

Pembahasan

Untuk titik dirotasi maka hasil transformasinya menjadi Maka; Diketahui: maka; Gunakan sifat invers matriks untuk memperoleh x dan y : Persamaan garis hasil rotasi adalah Jadi

Untuk titik begin mathsize 14px style A open parentheses x comma y close parentheses end style dirotasi begin mathsize 14px style R open square brackets 0 comma 0 close square brackets comma alpha end style maka hasil transformasinya menjadi

begin mathsize 14px style A equals open parentheses table row x row y end table close parentheses rightwards arrow with R open parentheses 0 comma 0 close parentheses comma alpha on top A to the power of apostrophe equals open parentheses table row cell x to the power of apostrophe end cell row cell y to the power of apostrophe end cell end table close parentheses equals open parentheses table row cell cos space alpha end cell cell negative sign sin space alpha end cell row cell sin space alpha end cell cell cos space alpha end cell end table close parentheses open parentheses table row x row y end table close parentheses end style   

Maka;

begin mathsize 14px style text x'=x cos α  -y sin α end text text y'=x sin α +y cos α end text end style   

Diketahui:

begin mathsize 14px style alpha equals 225 degree end style   maka;

begin mathsize 14px style sin space alpha equals minus sign 1 half square root of 2 end style   

begin mathsize 14px style cos space alpha equals minus sign 1 half square root of 2 end style   

begin mathsize 14px style open parentheses table row cell x to the power of apostrophe end cell row cell y to the power of apostrophe end cell end table close parentheses equals open parentheses table row cell negative sign 1 half square root of 2 end cell cell 1 half square root of 2 end cell row cell negative sign 1 half square root of 2 end cell cell negative sign 1 half square root of 2 end cell end table close parentheses open parentheses table row x row y end table close parentheses end style   

Gunakan sifat invers matriks untuk memperoleh x dan y :

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell open parentheses x apostrophe space y apostrophe close parentheses end cell equals cell negative sign 1 half square root of 2 open parentheses 1 space minus sign 1 space 1 space 1 close parentheses open parentheses space x space y close parentheses space space end cell row cell fraction numerator 1 over denominator open parentheses negative sign 1 close parentheses open parentheses negative sign 1 close parentheses minus sign left parenthesis minus sign 1 right parenthesis left parenthesis 1 right parenthesis end fraction minus sign open parentheses fraction numerator 2 over denominator square root of 2 end fraction close parentheses open parentheses 1 space 1 space minus sign 1 space 1 space close parentheses open parentheses x apostrophe space y apostrophe close parentheses space end cell equals cell open parentheses x space y close parentheses end cell row cell negative sign fraction numerator 1 over denominator square root of 2 end fraction open parentheses 1 space 1 space minus sign 1 space 1 close parentheses open parentheses space x apostrophe space y apostrophe close parentheses space end cell equals cell open parentheses x space y close parentheses space space space end cell row blank blank cell Maka space diperoleh space end cell row x equals cell negative sign fraction numerator 1 over denominator square root of 2 end fraction open parentheses x apostrophe plus y apostrophe close parentheses space end cell row y equals cell negative sign fraction numerator 1 over denominator square root of 2 end fraction open parentheses negative sign x apostrophe plus y apostrophe close parentheses space space end cell row cell 7 x and 4 y end cell equals cell 9 space end cell row cell negative sign fraction numerator 7 over denominator square root of 2 end fraction open parentheses x apostrophe plus y apostrophe close parentheses minus sign fraction numerator 4 over denominator square root of 2 end fraction open parentheses negative sign x apostrophe plus y apostrophe close parentheses end cell equals cell 9 space end cell row cell fraction numerator negative sign 3 x apostrophe over denominator square root of 2 end fraction minus sign fraction numerator 11 y to the power of apostrophe over denominator square root of 2 end fraction end cell equals cell 9 space end cell row cell 3 x apostrophe plus 11 y apostrophe end cell equals cell negative sign 9 square root of 2 end cell end table end style   

Persamaan garis hasil rotasi adalah  begin mathsize 14px style 3 x and 11 y equals minus sign 9 square root of 2 end style   

Jadi begin mathsize 14px style a and b equals 3 plus 11 equals 14. end style undefined   

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