16
QuizMultiple Choice

Dot Product and Work — Unit test

Question 16 • Precalculus

Let |u| = 4 at an angle of 210° and |v| = 9 at an angle of 315°, and w = u – v. What is the magnitude and direction angle of w?

Answer
A
|w| = 5.5; θ = 156.1°
B
|w| = 5.5; θ = 203.9°
C
|w| = 10.8; θ = 156.1°
D
|w| = 10.8; θ = 203.9°

Explanation

Convert each vector to components: u = (4 cos 210°, 4 sin 210°) ≈ (−3.46, −2.00), and v = (9 cos 315°, 9 sin 315°) ≈ (6.36, −6.36). Then w = u − v ≈ (−9.83, 4.36), so its magnitude is √[(−9.83)² + 4.36²] ≈ 10.8. Since w is in Quadrant II, its direction angle is about 156.1°, making the correct choice the vector with magnitude 10.8 and angle 156.1°.

AI-written and checked against the verified answer.

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