If `veca and vecb` are any two vectors of magnitudes 1and 2. respectively, and `(1-3veca.vecb)^(2)+|2veca+vecb+3(vecaxxvecb)|^(2)=47` then the angle between `veca and vecb ` isA. `pi//3`B. `pi-cos^(-1) (1//4)`C. `(2pi)/3`D. `cos^(-1) (1//4)`

If `veca and vecb` are any two vectors of magnitudes 1and 2. respectiv

1.	If `veca and vecb` are any two vectors of magnitudes 1and 2. respectively, and `(1-3veca.vecb)^(2)+\|2veca+vecb+3(vecaxxvecb)\|^(2)=47` then the angle between `veca and vecb ` isA. `pi//3`B. `pi-cos^(-1) (1//4)`C. `(2pi)/3`D. `cos^(-1) (1//4)`
Answer» Correct Answer - c ` 1 + 9 (veca .vecb)^(2) - 6( veca .vecb) + 4 \|veca\|^(2)` `+ \|vecb\|^(2) + 9 \|veca xx vecb\|^(2) + 4veca.vecb = 47` `or 1 + 4+4 +36 - 4 cos theta = 47` `or cos theta = -1/2` Hence, the angle between `veca and vecb is (2pi)/3`

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