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If f:A rarr B defined as f(x)=2sinx-2 co...

If `f:A rarr B` defined as `f(x)=2sinx-2 cos x+3sqrt2` is an invertible function, then the correct statement can be

A

`A=[(pi)/(4), (5pi)/(4)], B=[2sqrt2, 5sqrt5]`

B

`A=[(-pi)/(4),(5pi)/(4)], B=[sqrt2, 5sqrt2]`

C

`A=[(-pi)/(4), (3pi)/(4)],B=[sqrt2, 4,sqrt2]`

D

`A=[(-pi)/(4),(3pi)/(4)], B=[sqrt2, 5sqrt2]`

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The correct Answer is:
To solve the problem of determining the correct statement regarding the function \( f(x) = 2\sin x - 2\cos x + 3\sqrt{2} \) being an invertible function, we need to analyze the function's properties of being one-to-one (injective) and onto (surjective). ### Step-by-Step Solution: 1. **Understanding the Function**: The given function is \( f(x) = 2\sin x - 2\cos x + 3\sqrt{2} \). We need to check the behavior of this function over different intervals to determine if it is one-to-one and onto. **Hint**: Start by rewriting the function in a more manageable form. 2. **Rewriting the Function**: We can rewrite the trigonometric part of the function using the sine addition formula. Notice that: \[ 2\sin x - 2\cos x = 2(\sin x - \cos x) \] We can express \( \sin x - \cos x \) in terms of sine: \[ \sin x - \cos x = \sqrt{2}\left(\sin x \cdot \frac{1}{\sqrt{2}} - \cos x \cdot \frac{1}{\sqrt{2}}\right) = \sqrt{2}\sin\left(x - \frac{\pi}{4}\right) \] Therefore, we can rewrite \( f(x) \) as: \[ f(x) = 2\sqrt{2}\sin\left(x - \frac{\pi}{4}\right) + 3\sqrt{2} \] **Hint**: Identify the range of the sine function to understand the behavior of \( f(x) \). 3. **Analyzing the Range**: The sine function oscillates between -1 and 1. Thus, \[ 2\sqrt{2}\sin\left(x - \frac{\pi}{4}\right) \text{ oscillates between } -2\sqrt{2} \text{ and } 2\sqrt{2}. \] Adding \( 3\sqrt{2} \) shifts this range: \[ f(x) \text{ oscillates between } 3\sqrt{2} - 2\sqrt{2} \text{ and } 3\sqrt{2} + 2\sqrt{2} = \sqrt{2} \text{ and } 5\sqrt{2}. \] **Hint**: Determine the intervals where the function is one-to-one. 4. **Finding Intervals for Injectivity**: To ensure that \( f(x) \) is one-to-one, we need to restrict \( x \) to intervals where the sine function does not repeat values. A suitable interval is \( \left[ \frac{\pi}{4}, \frac{5\pi}{4} \right] \), where the sine function is decreasing. **Hint**: Check if the function is onto in the chosen interval. 5. **Checking Surjectivity**: Since \( f(x) \) maps from the interval \( \left[ \frac{\pi}{4}, \frac{5\pi}{4} \right] \) to the range \( [\sqrt{2}, 5\sqrt{2}] \), we need to ensure that every value in this range can be achieved by some \( x \) in the interval. Given the continuity of sine and the fact that it covers all values in this range, \( f(x) \) is onto. **Hint**: Conclude the properties of the function. 6. **Conclusion**: Since \( f(x) \) is both one-to-one and onto in the interval \( \left[ \frac{\pi}{4}, \frac{5\pi}{4} \right] \), it is invertible in this interval. ### Final Answer: The correct statement regarding the function \( f(x) \) being invertible is that it is bijective (both one-to-one and onto) in the interval \( \left[ \frac{\pi}{4}, \frac{5\pi}{4} \right] \).
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