Find the values of x that satisfy 3cos^2(x) - 1 = 0.

Practice Questions

Q1
Find the values of x that satisfy 3cos^2(x) - 1 = 0.
  1. π/3, 2π/3
  2. 0, π
  3. π/2, 3π/2
  4. 0, 2π

Questions & Step-by-Step Solutions

Find the values of x that satisfy 3cos^2(x) - 1 = 0.
Correct Answer: x = π/3 + 2kπ, 2π/3 + 2kπ (k ∈ Z)
  • Step 1: Start with the equation 3cos^2(x) - 1 = 0.
  • Step 2: Add 1 to both sides of the equation to isolate the term with cos^2(x). This gives you 3cos^2(x) = 1.
  • Step 3: Divide both sides by 3 to solve for cos^2(x). This results in cos^2(x) = 1/3.
  • Step 4: Take the square root of both sides to find cos(x). Remember to consider both the positive and negative roots. This gives you cos(x) = sqrt(1/3) and cos(x) = -sqrt(1/3).
  • Step 5: Find the angles x that correspond to cos(x) = sqrt(1/3) and cos(x) = -sqrt(1/3).
  • Step 6: The angles for cos(x) = sqrt(1/3) are x = π/3 and x = 5π/3 (since cos is positive in the first and fourth quadrants).
  • Step 7: The angles for cos(x) = -sqrt(1/3) are x = 2π/3 and x = 4π/3 (since cos is negative in the second and third quadrants).
  • Step 8: Combine all the solutions: x = π/3, 2π/3, 4π/3, and 5π/3.
  • Trigonometric Equations – The question tests the ability to solve equations involving trigonometric functions, specifically cosine.
  • Quadratic Form in Trigonometry – The equation is transformed into a quadratic form, requiring knowledge of how to manipulate and solve such equations.
  • Periodic Solutions – Understanding that trigonometric functions are periodic and finding all equivalent angles that satisfy the equation.
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