MCQ
જો $\left( {\vec a  \times \;\vec b } \right)\,\, \times \,\,\vec c \, = \,\vec a \,\, \times \,\,\left( {\vec b \,\, \times \,\,\vec c } \right)\,$જ્યાં $\overline a \,\,\,\overline b $ અને $\overline c $ કોઈ પણ ત્રણ સદીશો હોય કે જેથી $\overline a \,.\,\,\overline b \,\, \ne \,\,0,\,\overline b \,\,.\,\overline c \,\, \ne \,\,0$ તો $\overline a \,$ અને $\overline c \,\,$ એ  .....
  • A
    તેમની વચ્ચેનો ખૂણો $\pi/6$
  • B
    લંબ
  • C
    સમાંતર
  • D
    તેમની વચ્ચેનો ખૂણો $\pi /3$

Answer

$(\,\vec a \,\,\, \times \,\,\vec b \,)\,\,\, \times \,\,\vec c \,\,\, = \,\,\vec a \,\, \times \,\,(\vec b \,\,\, \times \,\vec c \,)\,\,\,$

$\,\,(\vec a \,\,.\,\,\vec c )\,\,\vec b \, - \,\,(\vec b \,\,.\,\,\vec c )\,\,\vec a $

$ = \,\,(\vec a \,\,.\,\,\vec c )\,\,\,\vec b \, - \,\,(\,\vec a \, .\,\,\,\vec b )\,\,\vec c \,\,$

$ \Rightarrow \,\,(\,\vec b \,.  \,\vec c )\,\,\vec a \,\, = \,\,(\,\vec a \,\,.\,\,\,\vec b )\,\vec c $ 

કે જેથી ${\vec a}$ એ $\vec c\,\,$ ને સમાંતર છે     

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