1.

A vector r of magnitude 3sqrt2 units which makes an angle of (pi)/(4) and (pi)/(2) with y and z-axis, respectively is

Answer»

`r= pm3hati+3hatj`
`r=3hati+3hatj`
`r=pm 3hati+3hatj`
None of these

Solution :Here, `m="cos"pi/4=1/sqrt(2)` and `n="cos"pi/2 =0`
Therefore, `l^(2)+m^(2)+n^(2)=1` [GIVEN]
`l^(2)+1/2 +0=1`
`IMPLIES l= pm 1/sqrt(2)`
Hence, the required VECTOR `r=3sqrt(2) (l HAT(i)+m hat(j)+n hat(k))` is given by `r=3sqrt(2) (pm 1/sqrt(2) hat(i) +1/sqrt(2) hat(j) + 0hat(k))=r= pm 3 hat(i)+3hat(j)`


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