Solving for All Values of x in (cos2x)/(sin3x-sinx) = 1

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In summary, the conversation is about solving for all values of x in the equation (cos2x)/(sin3x-sinx) = 1. The person is having difficulty solving it and has tried to solve it as a quadratic equation, but was unable to factor it. They are asking for help and have found a potential solution of sinx = 1/2, leading to two possible values for x. However, they are unsure if this solution is correct and would like confirmation. The other person suggests that they have not shown enough work to determine where they may have gone wrong.
  • #1
xtpacygax
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Solve for all values of x:

(cos2x)/(sin3x-sinx) = 1

I found this problem and am having an extremely tough time solving it. I gotten down to a quadratic equation a couple of times, but it wouldn't factor. I am really stumped and really need some help. Thanks in advance.
 
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  • #2
xtpacygax said:
Solve for all values of x:

(cos2x)/(sin3x-sinx) = 1

I found this problem and am having an extremely tough time solving it. I gotten down to a quadratic equation a couple of times, but it wouldn't factor. I am really stumped and really need some help. Thanks in advance.

Don't you know how to solve all quadratic equations?
 
  • #3
Yes, I know how to solve quadratic equations, but I would get a negative under the radical and it would be undefined so the equation would not be possible. I think I found an answer and would like if someone could confirm this.

For the final equation I got:

sinx = 1/2

and then I got:

x = (pi)/6 + 2(pi)k
x = 5(pi)/6 + 2(pi)k

(Sorry, I don't know how to make a pi symbol)
 
  • #4
You have shown really none of your work so it's impossible to say where you might have gone wrong. Reducing the orginal formula to sin x, I get a cubic equation which has an obvious root of sin x= 1/2 and the remaining quadratic is just 2x2- 1= 0!
 

1. What is the first step in solving this equation?

The first step in solving this equation is to simplify the left side by using trigonometric identities. In this case, we can use the double angle formula for cosine to rewrite cos2x as 1-2sin^2x. This will give us the equation (1-2sin^2x)/(sin3x-sinx) = 1.

2. How do I solve for all values of x?

To solve for all values of x, we need to use algebraic techniques to manipulate the equation and isolate the variable x. In this case, we can multiply both sides of the equation by the denominator (sin3x-sinx) to eliminate it on the left side. Then, we can use the quadratic formula to solve for sinx and find two solutions for x.

3. Can I use a calculator to solve this equation?

Yes, you can use a calculator to solve this equation. However, it is important to set your calculator to the correct mode (degrees or radians) and check your answers by plugging them back into the original equation.

4. Are there any restrictions on the values of x?

Yes, there are restrictions on the values of x in this equation. Since we are dealing with trigonometric functions, the values of x must satisfy the domain and range of these functions. In this case, sinx cannot be equal to 0 and 1/2, as these values would result in a division by zero or an imaginary number.

5. Can this equation be solved without using trigonometric identities?

Yes, it is possible to solve this equation without using trigonometric identities. However, it may be more difficult and time-consuming to do so. Using trigonometric identities can simplify the equation and make it easier to solve for x.

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