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if A={theta: cos theta gt -(1)/(2),0 le...

`if A={theta: cos theta gt -(1)/(2),0 le theta le pi }and `
`B={theta: sin thetagt(1)/(2) ,(pi)/(3) lt theta le pi}`then

A

`A cap B= {theta:pi//3le theta le 2pi//3}`

B

`A cap B= {theta:-pi//3le theta le 2pi//3}`

C

`A cap B= {theta:-5pi//6le theta le 5pi//6}`

D

`A cup B= {theta:0 letheta le pi//6}`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to find the intersection of the sets A and B defined by the given conditions. ### Step 1: Define Set A Set A is defined as: \[ A = \{ \theta : \cos \theta > -\frac{1}{2}, 0 \leq \theta \leq \pi \} \] To find the values of \(\theta\) that satisfy \(\cos \theta > -\frac{1}{2}\), we need to determine the angles where the cosine function is greater than \(-\frac{1}{2}\) within the interval \([0, \pi]\). ### Step 2: Find the critical points for Set A The cosine function equals \(-\frac{1}{2}\) at: \[ \theta = \frac{2\pi}{3} \] Thus, \(\cos \theta > -\frac{1}{2}\) when: \[ 0 \leq \theta < \frac{2\pi}{3} \] So, we can express Set A as: \[ A = \{ \theta : 0 \leq \theta < \frac{2\pi}{3} \} \] ### Step 3: Define Set B Set B is defined as: \[ B = \{ \theta : \sin \theta > \frac{1}{2}, \frac{\pi}{3} < \theta \leq \pi \} \] To find the values of \(\theta\) that satisfy \(\sin \theta > \frac{1}{2}\), we need to determine the angles where the sine function is greater than \(\frac{1}{2}\). ### Step 4: Find the critical points for Set B The sine function equals \(\frac{1}{2}\) at: \[ \theta = \frac{\pi}{6} \] Thus, \(\sin \theta > \frac{1}{2}\) when: \[ \frac{\pi}{6} < \theta < \frac{5\pi}{6} \] However, since we are restricted to \(\frac{\pi}{3} < \theta \leq \pi\), we need to find the overlap: - The interval for \(\sin \theta > \frac{1}{2}\) is \((\frac{\pi}{6}, \frac{5\pi}{6})\). - The interval for Set B is \((\frac{\pi}{3}, \pi]\). ### Step 5: Determine the intersection of Set A and Set B Now we need to find the intersection of Set A and Set B: - Set A: \(0 \leq \theta < \frac{2\pi}{3}\) - Set B: \(\frac{\pi}{3} < \theta \leq \pi\) The intersection will be: \[ A \cap B = \{ \theta : \frac{\pi}{3} < \theta < \frac{2\pi}{3} \} \] ### Final Answer Thus, the intersection of sets A and B is: \[ A \cap B = \left( \frac{\pi}{3}, \frac{2\pi}{3} \right) \] ---
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