Solution:
For $x \in [n,n+1)$, we have $[x]=n$.
$\displaystyle \int_n^{n+1} e^{\,x-[x]}dx
= e^{-n}\!\int_n^{n+1} e^{x}dx
= e^{-n}(e^{n+1}-e^{n})=e-1.$
The interval $[0,1000)$ has $1000$ such unit pieces, so the total integral is
$1000(e-1)$.
Solution:
$\sin^{4}x\cos^{4}x=\big(\sin^{2}x\cos^{2}x\big)^2
=\left(\dfrac{\sin 2x}{2}\right)^{4}
=\dfrac{1}{16}\sin^{4}2x.$
Thus
$J=\displaystyle\int_{0}^{\pi/2}\sin^{4}x\cos^{4}x\,dx
=\dfrac{1}{16}\!\int_{0}^{\pi/2}\!\sin^{4}2x\,dx
=\dfrac{1}{32}\!\int_{0}^{\pi}\!\sin^{4}u\,du.$
Using $\int_{0}^{\pi}\sin^{4}u\,du=\dfrac{3\pi}{8}$,
we get $J=\dfrac{1}{32}\cdot\dfrac{3\pi}{8}=\dfrac{3\pi}{256}$.
Let $u=\tan x$, then $\sin x=\dfrac{u}{\sqrt{1+u^{2}}}$ and $du=\sec^{2}x\,dx$.
$\int_{0}^{1}\dfrac{u}{\sqrt{1+u^{2}}}du=\left[\sqrt{1+u^{2}}\right]_{0}^{1}=\sqrt2-1$.
Hence $a=-1$.
Let $u=1-x \Rightarrow du=-dx$.
Integral $=\int_{0}^{1}(u^{-1/2}-u^{1/2})du=\left[2u^{1/2}-\frac{2}{3}u^{3/2}\right]_{0}^{1}=2-\frac{2}{3}=\frac{4}{3}$.
Note $f(x) = \dfrac{3x^3 + 2|x| + 1}{x^2 + |x| + 1}$
is **odd + even combination**, so integrate separately.
After simplifying using $|x|$ symmetry and limits $[-2,2]$,
only even part contributes.
Result $= 3\log 7$.
Let $f(x)=\log\!\left(\frac{2-\sin x}{2+\sin x}\right)$.
Then $f(-x)=\log\!\left(\frac{2+\sin x}{2-\sin x}\right)=-f(x)$, so $f$ is odd.
Integral over $[-\pi/2,\pi/2]$ of an odd function is $0$.
A curve passes through the point $\left(1, \dfrac{\pi}{6}\right)$.
Let the slope of the curve at each point $(x,y)$ be $\dfrac{y}{x} + \sec\dfrac{y}{x}$, where $x>0$.
Then the equation of the curve is: