Solving Trigonometric Equations?

In summary, the problem is to solve the equation sin(pi(x) + pi/3) = 1 over the interval [-1/3,2/3]. The solution involves using the trigonometric identity sin(a+b) = sin(a)cos(b) + sin(b)cos(a) and the fact that sin(x) = 1 when x = pi/2 + 2pi(n), where n is any integer. The solutions to the equation are x = -1/6 + 2/3n, where n is any integer.
  • #1
Neophyte
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Homework Statement


Solve sin^2(x) = cos^2(x) over the interval [0,2pi]

The Attempt at a Solution


sin^2(x) = cos^2(x)
sin^2(x) = 1-sin^2(x)
2sin^2(x) = 1
sin^2(x) = 1/2 = pi/6
sin(x) = sq root 1/2 = sq root pi/6

Unfortunately I am completely lost at this point and am not sure if I did that part correctly. If I did where would I go from here? Any help would be greatly appreciated, including any books where I could find some examples of whatever (or what) this is. Regardless, thank you for your time.
 
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  • #2
Where did pi/6 come from in your fourth equation?
 
  • #3
Sin(1/2) = pi/6
After I got lost I started adding things to see if I could make my own rules naturally. It has not seemed to work yet though.

Sorry figured out next few steps
sin = sq rt 1/2 = 1 sq rt 2 = sq rt 2/2 = pi/4

Thank you for helping me :).
 
Last edited:
  • #4
You got sin²(x) = ½. Now you have to figure out which x's in [0,2pi] satisfy this equation. One solution is pi/4. There are three more solutions.

Hint: Draw a picture.
 
  • #5
pi/4, 3pi/4, 5pi/4, 7pi/4

I appreciate the help.
 
  • #6
I am sorry to be a nuisance but I cannot seem to get this.
Homework Statement
sin(pi(x) + pi/3) = 1
over interval [-1/3,2/3]

Attemps
sin(pi(x))cos(pi/3) + sin(pi/3)cos(pi(x))
1. 0(1/2) + sq rt 3 /2 - 1 = 1
- sq rt 3 / 2 = 1

2. sin(2)(1/2) + sq rt 3 /2 cos(2)

3. Throw Things -> Cry
 
  • #7
I nearly resorted to step 3 as well :cry: until I had a revelation.

if sin(x)=1
then x=pi/2,5pi/2,-3pi/2 etc. = pi/2+2pi(n) , n being any integer

Therefore, sin(pi(x)+pi/3)=1

pi(x)+pi/3=pi/2+2pi(n)

I'm sure you can take it from here :smile:
 

1. What are trigonometric equations?

Trigonometric equations are mathematical expressions that involve trigonometric functions, such as sine, cosine, and tangent. These equations typically involve one or more variables and their corresponding trigonometric functions, and the goal is to solve for the values of the variables that make the equation true.

2. How do you solve trigonometric equations?

To solve a trigonometric equation, you must use algebraic methods to isolate the variable on one side of the equation. This may involve using trigonometric identities, factoring, or other techniques. Once the variable is isolated, you can use inverse trigonometric functions to find the value(s) of the variable.

3. What is the unit circle and how does it relate to solving trigonometric equations?

The unit circle is a circle with a radius of 1 that is centered at the origin of a graph. It is used in trigonometry to represent the values of trigonometric functions for different angles. When solving trigonometric equations, you may need to use the unit circle to find the values of the trigonometric functions for a given angle.

4. Are there any special cases when solving trigonometric equations?

Yes, there are a few special cases that may arise when solving trigonometric equations. These include equations with multiple solutions, equations with extraneous solutions, and equations with restricted domains. It is important to carefully check your solutions and consider the domain of the equation when solving trigonometric equations.

5. How can I check if my solution to a trigonometric equation is correct?

One way to check if your solution is correct is to plug the value(s) you found for the variable back into the original equation and see if it makes the equation true. You can also use a graphing calculator to graph the equation and your solution and see if they intersect at the correct point(s).

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