Question:
The shortest distance between the line $x-y=1$ and the curve $x^{2}=2 y$ is:
Correct Option:
Solution:
Shortest distance must be along common normal
$m_{1}($ slope of line $x-y=1)=1 \Rightarrow$ slope of perpendicular line $=-1 m_{2}=\frac{2 x}{2}=x \Rightarrow m_{2}=h \Rightarrow$
slope of normal $-\frac{1}{h}$
$-\frac{1}{h}=-1 \Rightarrow h=1$
sopoint is $\left(1, \frac{1}{2}\right)$
$\mathrm{D}=\left|\frac{1-\frac{1}{2}-1}{\sqrt{1+1}}\right|=\frac{1}{2 \sqrt{2}}$