just recall that orthogonal means that u•v = 0. So,
(a) (1,2)•(k,k) = k + 2k = 0, so k=0
(b) (1,2,1)•(k,2k,4) = k+4k+4 = 0, so k = -4/5
Kind of boring examples, IMO.
Determine all values of k for which each pair of vectors is orthogonal.
a) (1,2) and (k,k)
b) (1,2,1) and (k,2k,4)
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