Math Problem Statement

Let v = ⟨-5, 12⟩. What is the approximate direction angle of v?

23°

67°

113°

157°

Solution

To find the direction angle θ\theta of a vector v=5,12v = \langle -5, 12 \rangle, we can use the formula:

θ=tan1(yx)\theta = \tan^{-1} \left( \frac{y}{x} \right)

where x=5x = -5 and y=12y = 12.

  1. Calculate tan1(125)\tan^{-1} \left( \frac{12}{-5} \right):

    θ=tan1(125)tan1(2.4)\theta = \tan^{-1} \left( \frac{12}{-5} \right) \approx \tan^{-1}(-2.4)

    Using a calculator, we find:

    θ67.38\theta \approx -67.38^\circ

  2. Adjust for the correct quadrant:

    Since the vector 5,12\langle -5, 12 \rangle is in the second quadrant (negative xx-value and positive yy-value), we add 180° to the angle:

    θ=67.38+180112.62\theta = -67.38^\circ + 180^\circ \approx 112.62^\circ

Thus, the approximate direction angle is:

θ113\theta \approx 113^\circ

Answer: 113°

Would you like further details on this calculation or have additional questions?


Here are some related questions for further practice:

  1. What is the direction angle of a vector in the fourth quadrant?
  2. How would the direction angle change if the vector were 5,12\langle 5, -12 \rangle?
  3. Can you find the magnitude of v=5,12v = \langle -5, 12 \rangle?
  4. What is the direction angle of 12,5\langle 12, -5 \rangle?
  5. How do we interpret a negative angle in vector direction?

Tip: Remember, if the vector lies in the second or third quadrant, add 180° to the inverse tangent result to find the correct direction angle.

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Math Problem Analysis

Mathematical Concepts

Vector Analysis
Direction Angles
Inverse Trigonometric Functions

Formulas

θ = tan^(-1)(y / x)

Theorems

Inverse Tangent for Angle Calculation

Suitable Grade Level

Grades 10-12