Let $f(t) =
\begin{vmatrix}
\cos t & 1 & 1 \\
2\sin t & 2t & 1 \\
\sin t & t & t
\end{vmatrix}$,
then $\displaystyle \lim_{t \to 0}\dfrac{f(t)}{t^2}$ is equal to:
Expand the determinant using first row:
$f(t) = \cos t
\begin{vmatrix}
2t & 1 \\ t & t
\end{vmatrix}
- 1
\begin{vmatrix}
2\sin t & 1 \\ \sin t & t
\end{vmatrix}
+ 1
\begin{vmatrix}
2\sin t & 2t \\ \sin t & t
\end{vmatrix}$
Simplify and expand around $t \to 0$ using $\sin t \approx t$ and $\cos t \approx 1 - t^2/2$.
After simplification, $\dfrac{f(t)}{t^2} \to 3$.
$\boxed{\text{Answer: (D) 3}}$
Let $L = \left(\dfrac{x - 3}{x + 2}\right)^x
= \left(1 - \dfrac{5}{x + 2}\right)^x.$
Take $\ln L = x \ln\!\left(1 - \dfrac{5}{x + 2}\right).$
For large $x$, use $\ln(1 - y) \approx -y$.
So, $\ln L \approx x \left(-\dfrac{5}{x + 2}\right) \to -5.$
Hence, $L = e^{-5}.$
his is the derivative of $\sin x-\cos x$ at $x=\frac{\pi}{4}$.
$\,(\sin x-\cos x)'=\cos x+\sin x \Rightarrow \cos\frac{\pi}{4}+\sin\frac{\pi}{4}
=\tfrac{\sqrt2}{2}+\tfrac{\sqrt2}{2}=\sqrt2.$
Let $f(x)=x+x^{2}+\ldots+x^{10}-10$.
Then $f'(x)=1+2x+3x^{2}+\ldots+10x^{9}$.
At $x=1$, $f'(1)=1+2+3+\ldots+10=55$.
Hence limit $=\dfrac{f'(1)}{5}=\dfrac{55}{5}=11$.
$\dfrac{\sin x}{x}=1-\dfrac{x^2}{6}+O(x^4)<1$ for $x\ne0$ near $0$, and $>0$.
So $\left\lfloor \dfrac{\sin x}{x}\right\rfloor=0$ in a punctured neighborhood of $0$.
$1-\cos 2x=2\sin^2 x \Rightarrow \dfrac{\sqrt{1-\cos 2x}}{x}=\sqrt{2},\dfrac{|\sin x|}{x}$.
As $x\to0^+$, this $\to\sqrt{2}$; as $x\to0^-$, it $\to -\sqrt{2}$.
Thus two-sided limit does not exist; the right-hand limit is $\sqrt{2}$.
Let $\ln L = 2x \ln\left(1 + \frac{a}{x} + \frac{b}{x^2}\right)$
Using expansion $\ln(1+z) = z - \frac{z^2}{2} + \dots$
$\ln L = 2x\left(\frac{a}{x} + \frac{b}{x^2} - \frac{a^2}{2x^2}\right)$
$= 2a + \frac{2(b - a^2/2)}{x} + \dots$
As $x \to \infty$, $\ln L \to 2a$
Given $\ln L = 2 \Rightarrow 2a = 2 \Rightarrow a = 1$.
Hence, $b$ can be any real number.