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The number of ordered pair(s) (x, y) of...

The number of ordered pair(s) `(x, y)` of real numbers satisfying the equation `1+x^(2)+2x sin(cos^(-1)y)=0`, is :

A

0

B

1

C

2

D

3

Text Solution

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The correct Answer is:
To solve the equation \(1 + x^2 + 2x \sin(\cos^{-1} y) = 0\) for the number of ordered pairs \((x, y)\) of real numbers, we can follow these steps: ### Step 1: Rewrite the equation Start with the given equation: \[ 1 + x^2 + 2x \sin(\cos^{-1} y) = 0 \] Rearranging gives: \[ 1 + x^2 = -2x \sin(\cos^{-1} y) \] ### Step 2: Understand the range of \(\sin(\cos^{-1} y)\) Recall that \(\sin(\cos^{-1} y) = \sqrt{1 - y^2}\). This is valid for \(y\) in the range \([-1, 1]\). Therefore, we can rewrite the equation as: \[ 1 + x^2 = -2x \sqrt{1 - y^2} \] ### Step 3: Divide by \(x\) (assuming \(x \neq 0\)) If \(x \neq 0\), we can divide the entire equation by \(x\): \[ \frac{1}{x} + x = -2\sqrt{1 - y^2} \] ### Step 4: Analyze the left-hand side The left-hand side, \(\frac{1}{x} + x\), is a function of \(x\). To find its behavior, we can analyze it: - As \(x \to 0^+\), \(\frac{1}{x} \to +\infty\). - As \(x \to 0^-\), \(\frac{1}{x} \to -\infty\). - As \(x \to +\infty\), \(\frac{1}{x} \to 0\) and \(x \to +\infty\) implies the left side approaches \(+\infty\). - As \(x \to -\infty\), \(\frac{1}{x} \to 0\) and \(x \to -\infty\) implies the left side approaches \(-\infty\). ### Step 5: Determine the range of the left-hand side The function \(\frac{1}{x} + x\) has a minimum value. To find the critical points, we differentiate: \[ f(x) = \frac{1}{x} + x \] \[ f'(x) = -\frac{1}{x^2} + 1 \] Setting \(f'(x) = 0\) gives: \[ 1 = \frac{1}{x^2} \implies x^2 = 1 \implies x = 1 \text{ or } x = -1 \] Evaluating \(f(x)\) at these points: - \(f(1) = 1 + 1 = 2\) - \(f(-1) = -1 + 1 = 0\) ### Step 6: Analyze the right-hand side The right-hand side is \(-2\sqrt{1 - y^2}\). The maximum value of \(-2\sqrt{1 - y^2}\) occurs when \(y = 0\): \[ -2\sqrt{1 - 0^2} = -2 \] The minimum value occurs when \(y = \pm 1\): \[ -2\sqrt{1 - 1^2} = 0 \] Thus, the right-hand side ranges from \(-2\) to \(0\). ### Step 7: Find intersections We need to find where \(\frac{1}{x} + x\) intersects \(-2\sqrt{1 - y^2}\): - The minimum of \(\frac{1}{x} + x\) is \(0\) at \(x = -1\). - The maximum of \(-2\sqrt{1 - y^2}\) is \(-2\). ### Conclusion Since the minimum value of \(\frac{1}{x} + x\) (which is \(0\)) is greater than the maximum value of \(-2\sqrt{1 - y^2}\) (which is \(-2\)), there are no real solutions for \(x\) and \(y\) that satisfy the equation. Thus, the number of ordered pairs \((x, y)\) of real numbers satisfying the equation is: \[ \boxed{1} \]
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