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# C4 help watch

1. Part c, I don't know why they used:
.(3i -j +2k)
(file a3 is the question and a3so is the solution)
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2. You found that q=2, so the direction vector of l is (3, -1, 2). Since OC is perpendicular to l, then:
OC . direction vector of l = 0
3. One more thing:
dx/du = 2u
Can this be written as: dx = 2u du ?
4. (Original post by [email protected])
One more thing:
dx/du = 2u
Can this be written as: dx = 2u du ?
Yes, for all intents and purposes.

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