1.

The angle between two vectors `vec(A)= 3hat(i)+4hat(j)+5hat(k)` and `vec(B)= 3hat(i)+4hat(j)+5hat(k)` isA. `90^(@)`B. `0^(@)`C. `60^(@)`D. `45^(@)`

Answer» Correct Answer - A
`cos theta = (vec(A).vec(B))/(|A||B|)= ((3hat(i)+4hat(j)+5hat(k))(3hat(i)+4hat(j)-5hat(k)))/(sqrt(9+16+25)sqrt(9+16+25))`
`(9+16-25)/(50)=0`
`implies cos theta= 0, :. theta= 90^(@)`


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