The sum of all values of θ∈[0,2π]\theta \in [0, 2\pi] satisfying 2sin⁡2θ=cos⁡2θ2\sin^2 \theta = \cos 2\theta and 2cos⁡2θ=3sin⁡θ2\cos^2 \theta = 3\sin \theta is:

Answer: π\pi

Step-by-step solution

Step 1: Simplify the first equation

We are given two trigonometric equations. Let's simplify the first equation using the double angle identity for cosine, cos⁡2θ=1−2sin⁡2θ\cos 2\theta = 1 - 2\sin^2 \theta. Substituting this into the first equation will help us find the possible values of sin⁡θ\sin \theta.

Step 2: Solve for sin⁡θ\sin \theta from the first equation

After substituting the identity, we rearrange the terms to solve for sin⁡2θ\sin^2 \theta. This gives us sin⁡2θ=14\sin^2 \theta = \frac{1}{4}, which means sin⁡θ\sin \theta can be either 12\frac{1}{2} or −12-\frac{1}{2}.

Step 3: Simplify the second equation

Now, let's simplify the second equation. We can use the identity cos⁡2θ=1−sin⁡2θ\cos^2 \theta = 1 - \sin^2 \theta to express the equation entirely in terms of sin⁡θ\sin \theta. This will allow us to check which values of sin⁡θ\sin \theta from the previous step satisfy this equation.

Step 4: Solve for sin⁡θ\sin \theta from the second equation

Substitute cos⁡2θ=1−sin⁡2θ\cos^2 \theta = 1 - \sin^2 \theta into the second equation. This results in a quadratic equation in terms of sin⁡θ\sin \theta. Let x=sin⁡θx = \sin \theta, so the equation becomes 2x2+3x−2=02x^2 + 3x - 2 = 0.

Step 5: Solve the quadratic equation for sin⁡θ\sin \theta

We can factor the quadratic equation 2sin⁡2θ+3sin⁡θ−2=02\sin^2 \theta + 3\sin \theta - 2 = 0 into (2sin⁡θ−1)(sin⁡θ+2)=0(2\sin \theta - 1)(\sin \theta + 2) = 0. This gives two possible values for sin⁡θ\sin \theta: 12\frac{1}{2} or −2-2. Since the range of sin⁡θ\sin \theta is [−1,1][-1, 1], sin⁡θ=−2\sin \theta = -2 is not a valid solution.

Step 6: Find common solutions for sin⁡θ\sin \theta

Comparing the solutions from both equations, the only common value for sin⁡θ\sin \theta is 12\frac{1}{2}. We need to find all values of θ\theta in the interval [0,2π][0, 2\pi] for which sin⁡θ=12\sin \theta = \frac{1}{2}.

Step 7: Find θ\theta values and their sum

In the interval [0,2π][0, 2\pi], the values of θ\theta for which sin⁡θ=12\sin \theta = \frac{1}{2} are π6\frac{\pi}{6} (in the first quadrant) and 5π6\frac{5\pi}{6} (in the second quadrant). The sum of these values is π6+5π6=6π6=π\frac{\pi}{6} + \frac{5\pi}{6} = \frac{6\pi}{6} = \pi.

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