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Find a vector ` vec r`of magnitude `3sqrt(2)`units which makes an angle of `pi/4`and `pi/2`with `y`and z-axis respectively.A. `r= pm 3hati+3hatj`B. `r=3hati+3hatj`C. `r=pm 3hati+3hatj`D. None of these |
Answer» Correct Answer - A 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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