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Yukti Vault

Vector Algebra - JEE Mathematics question (AIEEE 2005 (Offline))

AIEEE 2005 (Offline)Question 1
For any vector $\vec a$, the value of $\left(\vec a\times\hat i\right)^{2}+\left(\vec a\times\hat j\right)^{2}+\left(\vec a\times\hat k\right)^{2}$ is equal to :
Vector Algebra
Options for question 1, choose one

Solution

$|\vec a\times\hat i|^2=a^2-a_1^2$, etc.; summing gives $3a^2-a^2=2a^2$.

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