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#1 2007-08-23 06:10:03

nate
Guest

relearning some Geometry, help on a problem

We have a right triangle with sides a, b, c=hypotenuse.  a=2x b=x c=10  I need to find the area for the triangle. 

Now its been a few (10) years since I have worked much with geometry, but if I can remember right I would start using pythagorean theorem and solve for x. Then use that number to find the area of the triangle. A=1/2(b*h).  Now the area is supposed to be 20.  I however can not seem to solve this and come up with the correct answer for x.  Any help? maybe Im looking too much into this

#2 2007-08-23 06:18:00

mikau
Member
Registered: 2005-08-22
Posts: 1,504

Re: relearning some Geometry, help on a problem

well we need to find what x is first so we can determine the side lengths, and then find the area.

By the pythagorean theorem we have that a^2 + b^2 = c^2 so (2x)^2 + x^2 = 10^2 this gives us
5x^2 = 100 so x^2 = 20 and x = sqrt(20) which is the same as 2*sqrt(5). The formula for area of a triangle is base times height divided by 2. Or a*b/2. So we have area =  4sqrt(5)*2sqrt(5)/2 = 4*sqrt(5)*sqrt(5) = 4*5 = 20.


A logarithm is just a misspelled algorithm.

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#3 2007-08-23 06:23:19

bossk171
Member
Registered: 2007-07-16
Posts: 305

Re: relearning some Geometry, help on a problem

a = x
b = 2x
c = 10

EDIT:

AHHH, mikau beat me.

Last edited by bossk171 (2007-08-23 06:24:40)


There are 10 types of people in the world, those who understand binary, those who don't, and those who can use induction.

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#4 2007-08-23 06:31:39

mikau
Member
Registered: 2005-08-22
Posts: 1,504

Re: relearning some Geometry, help on a problem

hehehe! want to race again? toss another problem at us, nate!


A logarithm is just a misspelled algorithm.

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#5 2007-08-23 07:05:30

nate
Guest

Re: relearning some Geometry, help on a problem

I was forgetting to square the 2 in 2x...

but thats what happens when you learn geometry over tens years ago and have to relearn it in 30 days

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