If a → = i ˙ ^ + j ˙ ^ + k ^ ,   b → = i ˙ ^ + 3 j ˙ ^ + 5 k ^ and c…

If a=i˙^+j˙^+k^, b=i˙^+3j˙^+5k^ and c=7i˙^+9j˙^+11k^ then the area of parallelogram having diagonals a+b and b+c is
  1. 46 sq units
  2. 1221 sq units
  3. 62sq units
  4. 6 sq units

Solution

Let A=a+b=i˙^+j˙^+k^+i˙^+3j˙^+5k^

=2i˙^+4j˙^+6k^

and B=b+c=i˙^+3j˙^+5k^+7i˙^+9j˙^+11k^

=8i˙^+12j˙^+16k^

Area of parallelogram=12||A×B||

=12i˙^j˙^k^24681216

=12|-8i˙^+16j˙^-8k^|

=(-4)2+(8)2+(-4)2

=46 sq units

Asked in: MHT CET Full Test 12

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