PROBLEM
15. Solve 3sin2x−1=0 on the interval x∈[0,2π].
STEP 1
1. The equation 3sin2x−1=0 is a trigonometric equation.
2. We are solving for x within the interval [0,2π].
3. The function sin2x has a period of π.
STEP 2
1. Isolate the trigonometric function sin2x.
2. Solve the equation sin2x=31.
3. Find all solutions for 2x within the interval [0,4π].
4. Solve for x by dividing the solutions for 2x by 2.
5. Ensure all solutions for x fall within the interval [0,2π].
STEP 3
First, isolate sin2x by adding 1 to both sides and then dividing by 3:
3sin2x−1=0 3sin2x=1 sin2x=31
STEP 4
Solve the equation sin2x=31. We need to find the general solutions for 2x:
The general solution for sinθ=a is given by:
θ=arcsin(a)+2kπorθ=π−arcsin(a)+2kπ For sin2x=31, we have:
2x=arcsin(31)+2kπ 2x=π−arcsin(31)+2kπ
STEP 5
Find all solutions for 2x within the interval [0,4π]:
1. Calculate arcsin(31). Let's denote it as α.
2. The solutions for 2x are:
- 2x=α+2kπ
- 2x=π−α+2kπ
For k=0:
- 2x=α
- 2x=π−α
For k=1:
- 2x=α+2π
- 2x=π−α+2π
Check which solutions fall within [0,4π].
STEP 6
Calculate specific values for 2x and check the interval:
1. 2x=α
2. 2x=π−α
3. 2x=α+2π
4. 2x=π−α+2π
Assuming α=arcsin(31), compute the approximate values and ensure they fall within [0,4π].
STEP 7
Solve for x by dividing each valid 2x solution by 2:
1. x=2α
2. x=2π−α
3. x=2α+2π
4. x=2π−α+2π
SOLUTION
Ensure all solutions for x fall within the interval [0,2π]:
Verify each calculated x value is within the interval [0,2π].
The solutions for x are approximately:
x=2arcsin(31),2π−arcsin(31),2arcsin(31)+2π,2π−arcsin(31)+2π
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