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Let the maximum value of $(\sin^{-1} x)^2 + (\cos^{-1} x)^2$ for $x \in \left[-\frac{\sqrt{3}}{2}, \frac{1}{\sqrt{2}}\right]$ be $\frac{m}{n} \pi^2$, where $\gcd(m, n) = 1$. Then $m + n$ is equal to __________.

Let the expression be $f(x) = (\sin^{-1} x)^2 + (\cos^{-1} x)^2$. We are given the domain $x \in \left[-\frac{\sqrt{3}}{2}, \frac{1}{\sqrt{2}}\right]$. The maximum value is given in the form $\frac{m}{n} \pi^2$, and we need to find $m + n$.

Function Simplification

Using the identity $\sin^{-1} x + \cos^{-1} x = \frac{\pi}{2}$, we can write $\cos^{-1} x = \frac{\pi}{2} - \sin^{-1} x$. Let $y = \sin^{-1} x$. Substituting this into the expression for $f(x)$: $f(x) = y^2 + \left(\frac{\pi}{2} - y\right)^2$ $f(x) = y^2 + \left(\frac{\pi^2}{4} - \pi y + y^2\right)$ $f(x) = 2y^2 - \pi y + \frac{\pi^2}{4}$ Let $g(y) = 2y^2 - \pi y + \frac{\pi^2}{4}$.

Domain Range Mapping

The domain for $x$ is $\left[-\frac{\sqrt{3}}{2}, \frac{1}{\sqrt{2}}\right]$. We need to find the corresponding range for $y = \sin^{-1} x$. The function $\sin^{-1} x$ is an increasing function. When $x = -\frac{\sqrt{3}}{2}$, $y = \sin^{-1}\left(-\frac{\sqrt{3}}{2}\right) = -\frac{\pi}{3}$. When $x = \frac{1}{\sqrt{2}}$, $y = \sin^{-1}\left(\frac{1}{\sqrt{2}}\right) = \frac{\pi}{4}$. So, the range for $y$ is $\left[-\frac{\pi}{3}, \frac{\pi}{4}\right]$.

Quadratic Maximum Value

We need to find the maximum value of the quadratic function $g(y) = 2y^2 - \pi y + \frac{\pi^2}{4}$ on the interval $y \in \left[-\frac{\pi}{3}, \frac{\pi}{4}\right]$. The graph of $g(y)$ is a parabola opening upwards (since the coefficient of $y^2$ is $2 > 0$). The vertex of the parabola occurs at $y = -\frac{b}{2a} = -\frac{(-\pi)}{2(2)} = \frac{\pi}{4}$. Since the vertex is at the right endpoint of the interval $\left[-\frac{\pi}{3}, \frac{\pi}{4}\right]$ and the parabola opens upwards, the function $g(y)$ is decreasing over this interval. Therefore, the maximum value of $g(y)$ occurs at the left endpoint, $y = -\frac{\pi}{3}$.

Result Calculation

Substitute $y = -\frac{\pi}{3}$ into $g(y)$: $g\left(-\frac{\pi}{3}\right) = 2\left(-\frac{\pi}{3}\right)^2 - \pi\left(-\frac{\pi}{3}\right) + \frac{\pi^2}{4}$ $g\left(-\frac{\pi}{3}\right) = 2\left(\frac{\pi^2}{9}\right) + \frac{\pi^2}{3} + \frac{\pi^2}{4}$ To add these fractions, find a common denominator, which is 36: $g\left(-\frac{\pi}{3}\right) = \frac{2 \times 4 \pi^2}{9 \times 4} + \frac{\pi^2 \times 12}{3 \times 12} + \frac{\pi^2 \times 9}{4 \times 9}$ $g\left(-\frac{\pi}{3}\right) = \frac{8\pi^2}{36} + \frac{12\pi^2}{36} + \frac{9\pi^2}{36}$ $g\left(-\frac{\pi}{3}\right) = \frac{(8 + 12 + 9)\pi^2}{36} = \frac{29\pi^2}{36}$. This maximum value is given as $\frac{m}{n} \pi^2$. Equating the two, we get $\frac{m}{n} = \frac{29}{36}$. We have $m = 29$ and $n = 36$. Check the condition $\gcd(m, n) = 1$: $\gcd(29, 36) = 1$, as 29 is prime. Finally, calculate $m + n$: $m + n = 29 + 36 = 65$.

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Similar Questions

  1. Let $\cos(\alpha + \beta) = -\frac{1}{10}$ and $\sin(\alpha - \beta) = \frac{3}{8}$, where $0 < \alpha < \frac{\pi}{3}$ and $0 < \beta < \frac{\pi}{4}$. If $\tan 2\alpha = \frac{3(1 - r\sqrt{5})}{\sqrt{11}(s + \sqrt{5})}, r, s \in \mathbb{N}$, then $r+s$ is equal to ________.

  2. The number of elements in the set $\{x \in [0, 180^\circ] : \tan(x + 100^\circ) = \tan(x + 50^\circ) \tan x \tan(x - 50^\circ)\}$ is _______.
  3. If $\frac{\pi}{4} + \sum_{p=1}^{11} \tan^{-1} \left( \frac{2^{p-1}}{1 + 2^{2p-1}} \right) = \alpha$, then $\tan \alpha$ is equal to _________.
  4. Let $\vec{a_k} = (\tan \theta_k) \hat{i} + \hat{j}$ and $\vec{b_k} = \hat{i} - (\cot \theta_k) \hat{j}$, where $\theta_k = \frac{2^{k - 1}\pi}{2^n + 1}$, for some $n \in \mathbb{N}, n > 5$. Then the value of $\frac{\sum_{k=1}^n |\vec{a_k}|^2}{\sum_{k=1}^n |\vec{b_k}|^2}$ is _____.

  5. If $k = \tan\left(\frac{\pi}{4} + \frac{1}{2}\cos^{-1}\left(\frac{2}{3}\right)\right) + \tan\left(\frac{1}{2}\sin^{-1}\left(\frac{2}{3}\right)\right)$, then the number of solutions of the equation $\sin^{-1}(kx-1) = \sin^{-1}x - \cos^{-1}x$ is ________
  6. The angle of elevation of the top $P$ of a vertical tower for a person standing at a point $A$ on the horizontal ground due north of the tower is $45^\circ$. Another person $B$ is standing $50$ m west of $A$ on the ground. If the angle of elevation of $P$ at $B$ is $30^\circ$ then the height (in meters) of the tower is
  7. Let $S = \{\theta \in [0,2\pi] - (\frac{\pi}{2}, \frac{3\pi}{2}) \mid \sin^{-1}(\sin\theta) + \cos^{-1}(\cos\theta) + \tan^{-1}(\tan\theta) = \frac{4\pi}{5}\}$ Then $\frac{30}{\pi} \sum_{\theta \in S} \theta$ is equal to ________
  8. If $y=\cos\left(\frac{\pi}{3}+\cos^{-1}\frac{x}{2}\right)$, then $(x-y)^2+3y^2$ is equal to ____________.

  9. Let A(4, -2), B(1, 1) and C(9, -3) be the vertices of a triangle ABC. Then the maximum area of the parallelogram AFDE, formed with vertices D, E and F on the sides BC, CA and AB of the triangle ABC respectively, is ______________.

  10. If $\text{A} = \frac{\sin 3^\circ}{\cos 9^\circ} + \frac{\sin 9^\circ}{\cos 27^\circ} + \frac{\sin 27^\circ}{\cos 81^\circ}$ and $\text{B} = \tan 81^\circ - \tan 3^\circ$, then $\frac{\text{B}}{\text{A}}$ is equal to _____.

Important Questions from Trigonometry

  1. Let $\cos(\alpha + \beta) = -\frac{1}{10}$ and $\sin(\alpha - \beta) = \frac{3}{8}$, where $0 < \alpha < \frac{\pi}{3}$ and $0 < \beta < \frac{\pi}{4}$. If $\tan 2\alpha = \frac{3(1 - r\sqrt{5})}{\sqrt{11}(s + \sqrt{5})}, r, s \in \mathbb{N}$, then $r+s$ is equal to ________.

  2. The number of elements in the set $\{x \in [0, 180^\circ] : \tan(x + 100^\circ) = \tan(x + 50^\circ) \tan x \tan(x - 50^\circ)\}$ is _______.
  3. If $\frac{\pi}{4} + \sum_{p=1}^{11} \tan^{-1} \left( \frac{2^{p-1}}{1 + 2^{2p-1}} \right) = \alpha$, then $\tan \alpha$ is equal to _________.
  4. Let $\vec{a_k} = (\tan \theta_k) \hat{i} + \hat{j}$ and $\vec{b_k} = \hat{i} - (\cot \theta_k) \hat{j}$, where $\theta_k = \frac{2^{k - 1}\pi}{2^n + 1}$, for some $n \in \mathbb{N}, n > 5$. Then the value of $\frac{\sum_{k=1}^n |\vec{a_k}|^2}{\sum_{k=1}^n |\vec{b_k}|^2}$ is _____.

  5. If $k = \tan\left(\frac{\pi}{4} + \frac{1}{2}\cos^{-1}\left(\frac{2}{3}\right)\right) + \tan\left(\frac{1}{2}\sin^{-1}\left(\frac{2}{3}\right)\right)$, then the number of solutions of the equation $\sin^{-1}(kx-1) = \sin^{-1}x - \cos^{-1}x$ is ________
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