Vectors - The Basics — Question 2

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Question 2

A vector in the plane has magnitude 1212, points into Quadrant II, and makes an angle of 35∘35^\circ with the negative xx-axis. Write it in component form.

Original worksheet page 1: question and worked solution for 5-1-002
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Question 2 – Solution

Identify the initial and terminal information first. Build the vector by subtracting coordinates, then use the magnitude formula or normalize only after the components are correct.

See the diagram in the original worksheet below.

Its standard-position angle is 180∘−35∘=145∘180^\circ-35^\circ=145^\circ.

Use v→=∥v→∥⟨cos⁡θ,sin⁡θ⟩\vec v=\|\vec v\|\langle\cos\theta,\sin\theta\rangle.

Thus v→=12⟨−cos⁡35∘,sin⁡35∘⟩\boxed{\vec v=12\langle-\cos35^\circ,\sin35^\circ\rangle}. The signs agree with Quadrant II.

The result follows from the defining vector formulas used above, and each component, magnitude, or scalar condition has been checked against the information in the question.

A vector separates two ideas: its components describe displacement, while its magnitude and unit vector describe size and direction. Always check signs and confirm that a unit vector has magnitude 11.

Original worksheet page 2: question and worked solution for 5-1-002

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