Question

A unit is represented as ( 0.8î +bj^ + 0.4k^) .the value of 'b' must be​

Answer 1

Since given vector is a unit vector, its magnitude must be 1.

$= > \sqrt{ {0.8}^{2} + {b}^{2} + {0.4}^{2} } = 1 \\ = > \frac{64}{100} + {b}^{2} + \frac{16}{100} = 1 \\ = > {b}^{2} = 1 - 0.8 = 0.2 \\ = > b = ±\sqrt{0.2}$

Hope, this helps...