Solving Sin(2x)+Sin(x)=0 over [0,2π)

In summary, the equation Sin(2x)+Sin(x)=0 over [0,2π) has four solutions: x=0, x=π/2, x=π, and x=3π/2. To solve this equation, you can use the trigonometric identity Sin(2x)=2Sin(x)Cos(x) and factor out Sin(x) to get the solutions Sin(x)=0 and Cos(x)=-1/2. The equation can be graphically represented as a sine wave with a frequency of 2 and a smaller amplitude, superimposed on a sine wave with a frequency of 1 and a larger amplitude. This equation has real-world applications in modeling periodic phenomena and in signal processing
  • #1
RansidMeat
1
0
hello there,
how do i solve over [0,2pi) for sin(2x)+sin(x)=0
thanks for what help you can give
RansidMeat
 
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  • #2
Yay, problem solved.

cookiemonster
 
  • #3
RansidMeat said:
hello there,
how do i solve over [0,2pi) for sin(2x)+sin(x)=0
thanks for what help you can give
RansidMeat
sin(2x) + sin(x) = 0
2sin(x)cos(x) + sin(x) = 0
2sin(x)cos(x) = -sin(x)
2cos(x) = -1 OR sin(x) = 0
cos(x) = -0.5 OR x = 0, pi
x = 2pi/3, 4pi/3 OR x = 0, pi
x = 0, (2/3)pi, pi, (4/3)pi.
 

1. What is the solution to the equation Sin(2x)+Sin(x)=0 over [0,2π)?

The solution to this equation is x=0, x=π/2, x=π, and x=3π/2.

2. How do you solve Sin(2x)+Sin(x)=0 over [0,2π)?

To solve this equation, you can use the trigonometric identity Sin(2x)=2Sin(x)Cos(x). This will allow you to rewrite the equation as 2Sin(x)Cos(x)+Sin(x)=0. From there, you can factor out Sin(x) to get Sin(x)(2Cos(x)+1)=0. This gives you the solutions of Sin(x)=0 and Cos(x)=-1/2. Using the unit circle, you can find the corresponding angles in the interval [0,2π] to get the solutions mentioned in the first question.

3. Can the equation Sin(2x)+Sin(x)=0 over [0,2π) have any other solutions?

No, the solutions mentioned in the first question are the only solutions for this equation in the given interval. However, the equation may have other solutions outside of this interval.

4. How can this equation be graphically represented?

This equation can be graphically represented as a sine wave with a frequency of 2 and a smaller amplitude, superimposed on a sine wave with a frequency of 1 and a larger amplitude. The points where the two waves intersect, or where the combined function crosses the x-axis, are the solutions to the equation.

5. Are there any real-world applications for this equation?

Yes, this equation can be used to model periodic phenomena such as the motion of a pendulum or the alternating current in an electrical circuit. It can also be used in signal processing and communication systems to analyze and manipulate signals with multiple frequencies.

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