Shortest Distance

I wonder what the shortest distance from any point to any graph of an equation is.

An example problem is: Find the shortest distance between $ (0,0) $ and $ y=\frac{x^2-3}{\sqrt{2}} $.

Solution to Example Problem: Any random point on the graph of the equation would be $(x,\frac{x^2-3}{\sqrt{2}})$ . Using the distance formula to find the distance between the origin and that graph, we simplify and get $d^2=(\frac{x^2-3}{\sqrt{2}})^2$ . Simplifying this further, we substitute $x^2$ with $a$ and get $a+(\frac{a-3}{\sqrt{2}})^2= a+\frac{a^2}{2} -3a+\frac{9}{2}=\frac{a^2}{2}-2a+\frac{9}{2}$ .

Now, we must complete the square, completing it in the form $a(a-b)^2+c$ , where $c$ is the minimum value. So $d^2=(a-2)^2+\frac{5}{2}$ . The minimum of $d^2=\frac{5}{2}$ . Therefore, the minimum of $d=\boxed{\frac{\sqrt{10}}{2}}$ .

#Geometry #Quadraticoptimization

Easy Math Editor

This discussion board is a place to discuss our Daily Challenges and the math and science related to those challenges. Explanations are more than just a solution — they should explain the steps and thinking strategies that you used to obtain the solution. Comments should further the discussion of math and science.

When posting on Brilliant:

Use the emojis to react to an explanation, whether you're congratulating a job well done , or just really confused .
Ask specific questions about the challenge or the steps in somebody's explanation. Well-posed questions can add a lot to the discussion, but posting "I don't understand!" doesn't help anyone.
Try to contribute something new to the discussion, whether it is an extension, generalization or other idea related to the challenge.
Stay on topic — we're all here to learn more about math and science, not to hear about your favorite get-rich-quick scheme or current world events.

Markdown	Appears as
`italics` or `_italics_`	italics
`bold` or `__bold__`	bold
- bulleted - list	bulleted list
1. numbered 2. list	numbered list
Note: you must add a full line of space before and after lists for them to show up correctly
paragraph 1 paragraph 2	paragraph 1 paragraph 2
`[example link](https://brilliant.org)`	example link
`> This is a quote`	This is a quote
# I indented these lines # 4 spaces, and now they show # up as a code block. print "hello world"	# I indented these lines # 4 spaces, and now they show # up as a code block. print "hello world"

Math	Appears as
Remember to wrap math in `$` ... `$` or `\[` ... `\]` to ensure proper formatting.
`2 \times 3`	$2 \times 3$
`2^{34}`	$2^{34}$
`a_{i-1}`	$a_{i-1}$
`\frac{2}{3}`	$\frac{2}{3}$
`\sqrt{2}`	$\sqrt{2}$
`\sum_{i=1}^3`	$\sum_{i=1}^3$
`\sin \theta`	$\sin \theta$
`\boxed{123}`	$\boxed{123}$

Comments

Isn't it interesting how the shortest distance from a point $(x_{1},y_{1})$ and line $y=mx+b$ is $\frac{|y_{1}-mx_{1}-b|}{\sqrt{m^2+1}}$ ?

Or if you have the points $(x_{1},y_{1})$ , and the line $Ax_{1}+By_{1}+C=0$ , the shortest distance between them is $\frac{|Ax_{1}+By_{1}+C|}{\sqrt{A^2+B^2 }}$ ?

Lucas Chen - 7 years, 5 months ago

In general, you can always do this, but it often requires calculus.

Samir Khan - 7 years, 5 months ago

Math	Appears as
Remember to wrap math in `\(` ... `\)` or `\[` ... `\]` to ensure proper formatting.
`2 \times 3`	$2 \times 3$
`2^{34}`	$2^{34}$
`a_{i-1}`	$a_{i-1}$
`\frac{2}{3}`	$\frac{2}{3}$
`\sqrt{2}`	$\sqrt{2}$
`\sum_{i=1}^3`	$\sum_{i=1}^3$
`\sin \theta`	$\sin \theta$
`\boxed{123}`	$\boxed{123}$