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Activity 9.3.6

Avg difficulty 2.5
  1. Let u⃗=⟨2,3⟩\vu = \langle 2,3\rangle and v⃗=⟨−1,2⟩\vv = \langle -1,2\rangle. Find ∥u⃗∥\vecmag{\vu}, ∥v⃗∥\vecmag{\vv}, and ∥u⃗+v⃗∥\vecmag{\vu+\vv}. Is it true that ∥u⃗+v⃗∥=∥u⃗∥+∥v⃗∥\vecmag{\vu+\vv} = \vecmag{\vu}+\vecmag{\vv}?

  2. Under what conditions will ∥w⃗1+w⃗2∥=∥w⃗1∥+∥w⃗2∥\vecmag{\vw_1+\vw_2} = \vecmag{\vw_1}+\vecmag{\vw_2}?

  3. With the vector u⃗=⟨2,3⟩\vu = \langle 2,3\rangle, find the lengths of 2u⃗2\vu, 3u⃗3\vu, and −2u⃗-2\vu, respectively, and use proper notation to label your results.

  4. In general, if tt is any scalar, how will ∥tw⃗∥\vecmag{t \vw} be related to ∥w⃗∥\vecmag{\vw}?

  5. Of the vectors ı^\vi, ȷ^\vj, and ı^+ȷ^\vi+\vj, which are unit vectors?

  6. Find a unit vector v⃗\vv whose direction is the same as u⃗=⟨−2,3⟩\vu = \langle -2, 3\rangle.

  7. Find a unit vector v⃗\vv in the opposite direction to u⃗=⟨−2,3⟩\vu = \langle -2, 3\rangle.

Long, Keller & Schlicker, Active Calculus Multivariable, §9.3 Vectors, Activity 9.3.6

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Adapted from Active Calculus Multivariable © 2013–2026 Nicholas Long, Mitchel T. Keller, and Steven Schlicker. Licensed under CC BY-SA 4.0. Source: Active Calculus Multivariable. Imported at revision 692c03c.