Coordinate Bashing

by Binomial-theorem, Jan 23, 2012, 1:06 AM

Is the meaning of life.

In $\triangle ABC$, $\angle C$ is a right angle. Point $M$ is the midpoint of $\overline{AB}$, point $N$ is the midpoint of $\overline{AC}$, and point $O$ is the midpoint of $\overline{AM}$ The perimeter of $\triangle ABC$ is $112$ and $ON=12.5$. What is the area of $MNCB$?
(Source: Mathcounts/Introduction to Geometry AoPS)

Solution
This post has been edited 4 times. Last edited by Binomial-theorem, Feb 19, 2012, 9:13 PM

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6 Comments

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coordinate bashing is oh so ugly.

Complex Number Bashing, Vector bashing and Barycentric Coordinate Bashing are cleaner and more powerful a lot of the time.

The one thing coordinate bashing is a lot better for though is finding lengths :p
This post has been edited 1 time. Last edited by dinoboy, Jan 23, 2012, 1:13 AM

by dinoboy, Jan 23, 2012, 1:13 AM

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Hm, or finding areas in this case?

by Binomial-theorem, Jan 23, 2012, 1:31 AM

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There's a second way (though pretty similar). Since we can see that $ON$ is one half of $MC$, $MC=25$, but since this is the median of right triangle, we have $AB=50 \implies AC+BC=62$. Let $AC=b, BC=a$. So then our area is $\frac{3ab}{8}$, which can be evaluated since we know $a^2+b^2=50^2, a+b=62$.

by GlassBead, Jan 23, 2012, 1:35 AM

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vectors are very good for finding areas due to dot products and stuff :D

by dinoboy, Jan 23, 2012, 1:55 AM

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You need something better to do with your life.

by dragon96, Jan 23, 2012, 4:27 AM

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Ohh, thanks for the recommendation. I'll go learn baycentric points or whatever they are called :D.
This post has been edited 3 times. Last edited by Binomial-theorem, Jan 23, 2012, 5:04 AM

by Binomial-theorem, Jan 23, 2012, 4:34 AM

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