The problem is to solve the equation $\sin(\theta - \frac{\pi}{3}) = -\frac{1}{2}$ for $0 \le \theta < 2\pi$.

AlgebraTrigonometryTrigonometric EquationsSine FunctionSolving Equations
2025/4/24

1. Problem Description

The problem is to solve the equation sin(θπ3)=12\sin(\theta - \frac{\pi}{3}) = -\frac{1}{2} for 0θ<2π0 \le \theta < 2\pi.

2. Solution Steps

Let x=θπ3x = \theta - \frac{\pi}{3}. The equation becomes sin(x)=12\sin(x) = -\frac{1}{2}. We are given the condition 0θ<2π0 \le \theta < 2\pi. This can be written as π3θπ3<2ππ3-\frac{\pi}{3} \le \theta - \frac{\pi}{3} < 2\pi - \frac{\pi}{3}, or π3x<5π3-\frac{\pi}{3} \le x < \frac{5\pi}{3}.
We need to find the angles xx in the interval [π3,5π3)[-\frac{\pi}{3}, \frac{5\pi}{3}) such that sin(x)=12\sin(x) = -\frac{1}{2}.
We know that sin(7π6)=12\sin(\frac{7\pi}{6}) = -\frac{1}{2} and sin(11π6)=12\sin(\frac{11\pi}{6}) = -\frac{1}{2}. We want to check if these angles are in the specified interval.
Since 7π6=76π1.167π\frac{7\pi}{6} = \frac{7}{6}\pi \approx 1.167\pi and 11π6=116π1.833π\frac{11\pi}{6} = \frac{11}{6}\pi \approx 1.833\pi, we have 0<7π6<5π30 < \frac{7\pi}{6} < \frac{5\pi}{3} and 0<11π6<5π30 < \frac{11\pi}{6} < \frac{5\pi}{3}. Also, π3<0-\frac{\pi}{3} < 0, so 7π6\frac{7\pi}{6} and 11π6\frac{11\pi}{6} are in the given interval.
Now, x=θπ3x = \theta - \frac{\pi}{3}. Therefore, θ=x+π3\theta = x + \frac{\pi}{3}.
When x=7π6x = \frac{7\pi}{6}, θ=7π6+π3=7π6+2π6=9π6=3π2\theta = \frac{7\pi}{6} + \frac{\pi}{3} = \frac{7\pi}{6} + \frac{2\pi}{6} = \frac{9\pi}{6} = \frac{3\pi}{2}.
When x=11π6x = \frac{11\pi}{6}, θ=11π6+π3=11π6+2π6=13π6\theta = \frac{11\pi}{6} + \frac{\pi}{3} = \frac{11\pi}{6} + \frac{2\pi}{6} = \frac{13\pi}{6}.
Since 0θ<2π0 \le \theta < 2\pi, we have 03π2<2π0 \le \frac{3\pi}{2} < 2\pi, so θ=3π2\theta = \frac{3\pi}{2} is a solution. Since 013π6=2π+π60 \le \frac{13\pi}{6} = 2\pi + \frac{\pi}{6}, we need to reduce it to an angle in the given interval, but 13π6\frac{13\pi}{6} is outside the range. However, 13π6=11π6+2π6=11π6+π3\frac{13\pi}{6} = \frac{11\pi}{6} + \frac{2\pi}{6} = \frac{11\pi}{6} + \frac{\pi}{3}, so θ=13π6\theta = \frac{13\pi}{6} is another solution for θ\theta.
However, we must have θ<2π\theta < 2\pi. Thus, θ=13π6>2π=12π6\theta = \frac{13\pi}{6} > 2\pi = \frac{12\pi}{6}. Then, since θ\theta must be less than 2π2\pi, and the interval of xx is [π3,5π3)[-\frac{\pi}{3}, \frac{5\pi}{3}), and we know sin(θπ3)=12\sin(\theta - \frac{\pi}{3}) = -\frac{1}{2}, the solutions are x=7π6x = \frac{7\pi}{6} and x=11π6x = \frac{11\pi}{6}. Hence θ=9π6=3π2\theta = \frac{9\pi}{6} = \frac{3\pi}{2} and θ=13π6\theta = \frac{13\pi}{6}. But 13π6>2π\frac{13\pi}{6} > 2\pi, so 13π6\frac{13\pi}{6} is not a solution.

3. Final Answer

θ=3π2\theta = \frac{3\pi}{2}

Related problems in "Algebra"

We are given that $a < b$. We need to determine the correct inequality sign (either $<$ or $>$) to f...

InequalitiesAlgebraic Manipulation
2025/6/26

The problem asks us to find the integer part $a$ and the fractional part $b$ of the number $\frac{2}...

RadicalsRationalizationSimplificationInteger PartFractional Part
2025/6/26

Given $x = \frac{1}{\sqrt{5}-\sqrt{3}}$ and $y = \frac{1}{\sqrt{5}+\sqrt{3}}$, we need to find the v...

Algebraic ManipulationRationalizationExponentsSimplificationSurds
2025/6/26

The problem asks us to rationalize the denominators of two expressions and choose the correct answer...

RationalizationRadicalsSimplificationExponents
2025/6/26

The problem asks us to evaluate four expressions and choose the correct answer from a set of options...

SimplificationRadicalsExponentsAlgebraic Expressions
2025/6/26

We are asked to find the values of the given expressions involving absolute values and radicals, and...

Absolute ValueRadicalsExpressionsSimplification
2025/6/26

We need to solve the following equations for $x$: 28. $\frac{4}{x+1} = \frac{7}{3x-2}$ 29. $\frac{x+...

Linear EquationsSolving EquationsFractional Equations
2025/6/25

We are asked to solve the following equations: 28. $\frac{4}{x+1} = \frac{7}{3x-2}$ 29. $\frac{x+1}{...

Linear EquationsSolving EquationsFractionsAlgebraic Manipulation
2025/6/25

We are asked to solve problem number 28 from the image, which is to find the value of $x$ in the equ...

Linear EquationsSolving EquationsFractions
2025/6/25

The problem is to solve the following equations for $x$: 19. $\frac{x}{2} - \frac{x}{5} = 3$ 20. $\f...

Linear EquationsSolving EquationsFractions
2025/6/25