The magnitude of the scalar projection of (1, m, 0) on (2, 2, 1) is 4. Determine the value of m.
Answer: 5 or -7.
I got 5 as my answer. How can it possibly be -7 as well?
Answer: 5 or -7.
I got 5 as my answer. How can it possibly be -7 as well?
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The tricky word is "magnitude". This is analogous to absolute value. So if the question said the absolute value of m+2 is 3, you have to solve m+2 = 3 and m+2 = -3 and your two answers would be 1 and -5.
So you need to solve two problems:
(1,m,0) dot (2,2,1) = 4 for which the answer is 5
and
(1,m,0) dot (2,2,1) = -4 for which the answer is -7
So you need to solve two problems:
(1,m,0) dot (2,2,1) = 4 for which the answer is 5
and
(1,m,0) dot (2,2,1) = -4 for which the answer is -7