If a unit vector is represented by `0.4 hati+0.7 hatj + chatk` then the value of c is

Options

A. `sqrt(0.25)`
B. `sqrt(0.30)`
C. `sqrt(0.35)`
D. `sqrt(0.40)`

Answer

C

Explanation

The magnitude of unit vector is 1
`because hatn = 0.4 hati + 0.7 hatj + c hatk`
`therefore sqrt ((0.4)^(2) + (0.7)^(2) + c^(2))=1`
`therefore sqrt (0.16 + 0.49 + c^(2)) =1`
`therefore 0.65 +c^(2) =1 therefore c^(2) =1-0.65 =0.35`
`therefore c= sqrt (0.35)`