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Let f(x) = [{:( sin (pi)/(2) x "," , 0 l...

Let f(x) = `[{:( sin (pi)/(2) x "," , 0 le x le 1) , (3 - 2x "," , x ge 1):}` then

A

f(x) has local maxima at x = 1

B

f(x) has local minima at x = 1

C

f(x) does not have any local extrema at x = 1

D

f(x) has a global minima at x = 1

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the piecewise function given: \[ f(x) = \begin{cases} \sin\left(\frac{\pi}{2} x\right) & \text{for } 0 \leq x \leq 1 \\ 3 - 2x & \text{for } x > 1 \end{cases} \] ### Step 1: Analyze the function on the interval \(0 \leq x \leq 1\) 1. **Find the derivative of \(f(x)\)** for \(0 \leq x \leq 1\): \[ f'(x) = \frac{d}{dx}\left(\sin\left(\frac{\pi}{2} x\right)\right) = \frac{\pi}{2} \cos\left(\frac{\pi}{2} x\right) \] 2. **Set the derivative to zero to find critical points**: \[ \frac{\pi}{2} \cos\left(\frac{\pi}{2} x\right) = 0 \] This occurs when: \[ \cos\left(\frac{\pi}{2} x\right) = 0 \implies \frac{\pi}{2} x = \frac{\pi}{2} + n\pi \quad (n \in \mathbb{Z}) \] The only solution in the interval \(0 \leq x \leq 1\) is: \[ x = 1 \] ### Step 2: Analyze the function at \(x = 1\) 1. **Evaluate \(f(1)\)**: \[ f(1) = \sin\left(\frac{\pi}{2} \cdot 1\right) = \sin\left(\frac{\pi}{2}\right) = 1 \] ### Step 3: Analyze the function for \(x > 1\) 1. **Evaluate \(f(x)\)** for \(x > 1\): \[ f(x) = 3 - 2x \] This is a linear function with a negative slope, which means it is decreasing for \(x > 1\). ### Step 4: Check the behavior around \(x = 1\) 1. **Evaluate \(f(1)\)** from both sides: - As \(x\) approaches \(1\) from the left (\(x \to 1^-\)): \[ f(1^-) = \sin\left(\frac{\pi}{2}\right) = 1 \] - As \(x\) approaches \(1\) from the right (\(x \to 1^+\)): \[ f(1^+) = 3 - 2(1) = 1 \] 2. **Determine if it is a local maximum or minimum**: - Since \(f(x)\) is increasing on \([0, 1]\) and then decreases for \(x > 1\), we conclude that \(f(x)\) has a local maximum at \(x = 1\). ### Conclusion The function \(f(x)\) has a local maximum at \(x = 1\) with a value of \(f(1) = 1\).
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