Trigonometry

posted by .

Use inverse trigonometric functions to find the solutions of the equation that are in the given interval, and approximate the solutions to four decimal places. (Enter your answers as a comma-separated list.)
cos(x)(9cos(x) + 4) = 4; [0, 2π)

  • Trigonometry -

    expand first
    9cos^2 x + 4cosx - 4 = 0
    let y = cosx
    9y^2 + 4y - 4 = 0
    y = (-4 ±√160)/18 , using the formula
    = (-4 + 4√10)/18
    = (-2 ± 2√10)/9
    = appr .480506 or appr -.92495

    then cosx = .480506 or cosx = -.92495
    x = 61.28° or 298.72° or 157.66° or 202.34°

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Trigonometry

    Use inverse trigonometric functions to find the solutions of the equation that are in the given interval, and approximate the solutions to four decimal places. (Enter your answers as a comma-separated list.) 10 sin^2 x = 3 sin x + …
  2. Trigonometry

    Use inverse trigonometric functions to find the solutions of the equation that are in the given interval, and approximate the solutions to four decimal places. (Enter your answers as a comma-separated list.) 10 sin^2 x = 3 sin x + …
  3. Trigonometry

    Use inverse trigonometric functions to find the solutions of the equation that are in the given interval, and approximate the solutions to four decimal places. (Enter your answers as a comma-separated list.) 10 sin^2 x = 3 sin x + …
  4. Calculus

    We can find some of the solutions of sin x = 0.2 graphically by graphing y = sin x and y = 0.2 (I was able to figure this one out) Use the graph below to estimate some of the solutions. (Let −3π < x < 3π.) Enter …
  5. Math

    We can find the solutions of sin x = 0.6 algebraically. (Round your answers to two decimal places.) (a) First we find the solutions in the interval [0, 2π). We get one such solution by taking sin−1 to get x = ________ (smaller …
  6. Pre-Cal

    Solve the given equation. (Enter your answers as a comma-separated list. Let k be any integer. Round terms to two decimal places where appropriate.) cos θ = −1/2 1).θ= Answer-->(2π/3)+2πn, 4π/3+2πn …
  7. Pre-Cal

    An equation is given. (Enter your answers as a comma-separated list. Round terms to three decimal places where appropriate. If there is no solution, enter NO SOLUTION.) 2 cos 2θ − 1 = 0 a). Find all solutions of the equations …
  8. Pre-Cal:(Cont.)

    [Note: I've tried this problem 4 times already and still have it wrong. I know the steps to doing it but for some reason its wrong. an someone please help me get these answers for (b).] An equation is given. (Enter your answers as …
  9. maths

    Use a graphing utility to approximate the solutions of the equation in the interval [0, 2Ï€). (Round your answers to three decimal places. Enter your answers as a comma-separated list.) 6 sin(x) + 3 cos(x) = 0
  10. Calculus

    Using inverse trigonometric functions, find a solution to the equation cos(x)=0.2 in the interval 0≤x≤4Ï€. Then, use a graph to find all other solutions to this equation in this interval. Enter your answers as a comma …

More Similar Questions