Let $f(x) = \cos^{-1}\left(\sqrt{\sin^{-1}\left(\sec\left(\ln\left(\frac{2x^2+3x-2}{x^2-3x+2}\right)\right)\right)}\right).$ Find the value of $1 + \left(\sum \alpha_i^2\right)$ where $\alpha_i$ represents the integers in the range of $f(x)$. If there are no integers in the range of $f(x)$, then enter your answer as zero.
Step-by-Step Solution
Key Concept: composition and range of inverse trigonometric functions
$\color{{blue}}{{\text{{Step 1:}}}}$ To find the range of $f(x)$, we start by simplifying the given function.
We have $f(x) = \cos^{-1}\left(\sqrt{\sin^{-1}\left(\sec\left(\ln\left(\frac{2x^2+3x-2}{x^2-3x+2}\right)\right)\right)}\right)$.
First, let's simplify the expression inside the logarithm:
$$\begin{aligned}
\frac{2x^2+3x-2}{x^2-3x+2} &= \frac{(2x-1)(x+2)}{(x-1)(x-2)} \\
&= \frac{2x-1}{x-1} \cdot \frac{x+2}{x-2}
\end{aligned}$$
$\color{{blue}}{{\text{{Step 2:}}}}$ Next, we consider the domain of the function to ensure that the expression inside the logarithm is positive.
For the expression $\frac{2x-1}{x-1} \cdot \frac{x+2}{x-2}$ to be positive, either both factors must be positive or both must be negative.
This leads to the conditions:
- $x > 1$ and $x > 2$, or
- $x < 1$ and $x < 2$.
However, since $x$ cannot be simultaneously greater than 1 and 2, and less than 1 and 2, we refine these conditions:
- $x > 2$, or
- $x < 1$.
$\color{{blue}}{{\text{{Step 3:}}}}$ Now, we analyze the behavior of the function $\sec\left(\ln\left(\frac{2x^2+3x-2}{x^2-3x+2}\right)\right)$.
As $x$ approaches 2 from the right, $\frac{2x-1}{x-1} \cdot \frac{x+2}{x-2}$ approaches $+\infty$, and $\ln\left(\frac{2x^2+3x-2}{x^2-3x+2}\right)$ also approaches $+\infty$.
Conversely, as $x$ approaches 1 from the left, $\frac{2x-1}{x-1} \cdot \frac{x+2}{x-2}$ approaches $-\infty$, and $\ln\left(\frac{2x^2+3x-2}{x^2-3x+2}\right)$ approaches $-\infty$.
Since $\sec(\theta)$ is defined for $-\frac{\pi}{2} < \theta < \frac{\pi}{2}$, the range of $\sec\left(\ln\left(\frac{2x^2+3x-2}{x^2-3x+2}\right)\right)$ will be $[-1, 1]$.
$\color{{blue}}{{\text{{Step 4:}}}}$ Considering the next part of the function, $\sin^{-1}\left(\sec\left(\ln\left(\frac{2x^2+3x-2}{x^2-3x+2}\right)\right)\right)$,
its range will also be $[-1, 1]$ because $\sin^{-1}$ is defined for inputs in $[-1, 1]$.
$\color{{blue}}{{\text{{Step 5:}}}}$ Finally, for $\cos^{-1}\left(\sqrt{\sin^{-1}\left(\sec\left(\ln\left(\frac{2x^2+3x-2}{x^2-3x+2}\right)\right)\right)}\right)$,
since $\cos^{-1}$ is defined for inputs in $[-1, 1]$, and the square root of a value in $[-1, 1]$ is in $[0, 1]$,
the range of $f(x)$ will be $[0, \frac{\pi}{2}]$.
$\color{{blue}}{{\text{{Step 6:}}}}$ The integers in the range of $f(x)$ are 0.
Thus, $\sum \alpha_i^2 = 0^2 = 0$.
Therefore, $1 + \left(\sum \alpha_i^2\right) = 1 + 0 = 1$.
Therefore: $1$
Correct Answer: 0