his is the derivative of $\sin x-\cos x$ at $x=\frac{\pi}{4}$.
$\,(\sin x-\cos x)'=\cos x+\sin x \Rightarrow \cos\frac{\pi}{4}+\sin\frac{\pi}{4}
=\tfrac{\sqrt2}{2}+\tfrac{\sqrt2}{2}=\sqrt2.$
4
$\displaystyle \lim_{h \to 0} \frac{\sqrt{x + h} - \sqrt{x}}{h}$ is equal to …
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 $=\dfrac{f'(1)}{5}=\dfrac{55}{5}=11$.
1
$\displaystyle \int_{1}^{x}(1+\log t)^{2}\,dt$ is equal to …
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 $a=-1$.
1
$\displaystyle \int_{0}^{1}\frac{x}{(1-x)^{1/2}}dx$ is equal to …
Let $u=1-x \Rightarrow du=-dx$.
Integral $=\int_{0}^{1}(u^{-1/2}-u^{1/2})du=\left[2u^{1/2}-\frac{2}{3}u^{3/2}\right]_{0}^{1}=2-\frac{2}{3}=\frac{4}{3}$.
1
$\displaystyle \int \sqrt{x}e^{\sqrt{x}}dx$ is equal to …