Tuesday

October 21, 2014

October 21, 2014

Posted by **Zach** on Monday, September 8, 2008 at 12:20am.

D = (Ax + By + C) / sqrt(A^2 + B^2)

So, would you start out by multiplying sqrt (A^2 + B^2) to both sides and then it would become:

sqrt (A^2 + B^2)D = Ax + By + C

Then square both sides,

D^2(A^2 + B^2) = (Ax + By + C)^2

Then I got lost, could someone direct me through this problem? Did I start out the right way? Thanks!

- Alegbra -
**drwls**, Monday, September 8, 2008 at 7:45amJust manipulating the equation for D will not constitute a proof that it is correct. You need to derive it somehow.

Try deriving an equation for a line through (x,y) that is perpendicular to the line Ax + By +C = 0. Then compute where the two lines intersect. Call that point (x', y'). Then compute the distance between (x,y) and (x',y').

A proof can be found here:

http://mathworld.wolfram.com/Point-LineDistance2-Dimensional.html

**Answer this Question**

**Related Questions**

Geometry - How do I find the distance between (-9,3) and (-1,-5) By using the ...

Trig/Pre-Cal - Show that the distance between the points (x,y) and the line Ax...

Math - 1.Find the distance between P(7, -4) and the line with equation x - 3y + ...

Algebra - Consider the points (3, –1) and (9, 2). (a) State the midpoint of the ...

distance formula - I need to find the distance between two points, (6,-3) and (-...

Physics - suppose that the separation between speakers A and B is 5.80 m and the...

Math - We are learning about proofs. We drew lines between noncollinear points. ...

geometry - We are learning about proofs. We drew lines between noncollinear ...

Math - Did I do this problem correctly? Find the distance between the given ...

Math Help please!! - Could someone show me how to solve these problems step by ...