Math Problem Statement

Solve the trigonometric equation for x in the interval [0, 2π): 2sin²(x) - 3sin(x) + 1 = 0.

Solution

The given trigonometric equation is:

2sin2(x)3sin(x)+1=02\sin^2(x) - 3\sin(x) + 1 = 0

We need to solve this equation for xx in the interval [0,2π)[0, 2\pi).

Step 1: Let u=sin(x)u = \sin(x)

This transforms the equation into a quadratic form: 2u23u+1=02u^2 - 3u + 1 = 0

Step 2: Solve the quadratic equation

We solve this quadratic equation using the quadratic formula: u=b±b24ac2au = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} For the equation 2u23u+1=02u^2 - 3u + 1 = 0, the coefficients are a=2a = 2, b=3b = -3, and c=1c = 1.

Substitute these values into the quadratic formula: u=(3)±(3)24(2)(1)2(2)u = \frac{-(-3) \pm \sqrt{(-3)^2 - 4(2)(1)}}{2(2)} u=3±984u = \frac{3 \pm \sqrt{9 - 8}}{4} u=3±14u = \frac{3 \pm \sqrt{1}}{4} u=3±14u = \frac{3 \pm 1}{4}

Thus, the two possible values for uu (which represent sin(x)\sin(x)) are: u1=3+14=1andu2=314=12u_1 = \frac{3 + 1}{4} = 1 \quad \text{and} \quad u_2 = \frac{3 - 1}{4} = \frac{1}{2}

Step 3: Solve for xx

  • For u1=1u_1 = 1, we solve sin(x)=1\sin(x) = 1: x=π2x = \frac{\pi}{2}
  • For u2=12u_2 = \frac{1}{2}, we solve sin(x)=12\sin(x) = \frac{1}{2}: x=π6,5π6x = \frac{\pi}{6}, \, \frac{5\pi}{6} (since sin(x)=12\sin(x) = \frac{1}{2} at these angles in the interval [0,2π)[0, 2\pi)).

Final Answer:

The solutions for xx are: x=π2,π6,5π6x = \frac{\pi}{2}, \frac{\pi}{6}, \frac{5\pi}{6}

Would you like more details or have any further questions?

Related Questions:

  1. How do you apply the quadratic formula to solve trigonometric equations?
  2. Why are there two solutions for sin(x)=12\sin(x) = \frac{1}{2}?
  3. What are the general solutions for sin(x)=1\sin(x) = 1 and sin(x)=12\sin(x) = \frac{1}{2}?
  4. How do we determine solutions in the interval [0,2π)[0, 2\pi)?
  5. What are some other methods for solving trigonometric equations?

Tip:

When solving trigonometric equations, it helps to first transform the equation into a quadratic or factorizable form if possible. This simplifies finding the roots.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Quadratic Equations
Trigonometric Identities

Formulas

Quadratic formula: x = (-b ± √(b² - 4ac)) / 2a
Sine values in specific intervals: sin(x) = 1 and sin(x) = 1/2

Theorems

Sine Function Theorem (solutions exist for specific angles)
Quadratic Formula Theorem (used to solve quadratic equations)

Suitable Grade Level

Grades 9-12