#Please solve this...

14 messages · Page 1 of 1 (latest)

wicked talon
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(a).
If v ∈ ℒ(w), that means v = kw for some constant w. In that case:
proj(w, v) = (v·w/(w·w))w = k(w·w/(w·w))w = kw = v
Thus, ℒ(v, w) = ℒ(v, proj(w, v)) = ℒ(w).
(b).
We have:
perp(w, v) = v - proj(w, v)
So:
ℒ(v, w) = ℒ(perp(w, v) + proj(w, v), w)
Since proj(w, v) and w are collinear:
ℒ(perp(w, v) + proj(w, v), w) = ℒ(perp(w, v), w)
We don't even need v to be outside of ℒ(w), this will always work. When v ∈ ℒ(w), that will further simplify to just ℒ(w).

wicked talon
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Yes, both seem to be true.

glad cliff
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Thank you!

wicked talon
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You're welcome!

glad cliff
wicked talon
wicked talon
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You're welcome!

ionic jackalBOT
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@glad cliff has given 1 rep to @wicked talon

wicked talon
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(c).
If s is a direction vector for the line, then ks for any nonzero constant k is also a direction.
But since we need a unit vector, there can only be two, just with different signs.
(d).
Two vectors have the same direction if their unit vector is the same (up to sign).

ionic jackalBOT
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@glad cliff has given 1 rep to @wicked talon

glad cliff