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Mathematics 22 Online
OpenStudy (anonymous):

GEOMETRY HELP PLEASE I AM DESPERATE

jimthompson5910 (jim_thompson5910):

what's your question?

OpenStudy (anonymous):

Prove the Converse of the Pythagorean Theorem. The converse of the Pythagorean thearom states that when the sum of the squares of the lengths of the legs of the triangle equals the squared length of the hypotenuse, the triangle is a right triangle.

OpenStudy (anonymous):

hello please help

jimthompson5910 (jim_thompson5910):

ok let me think

OpenStudy (anonymous):

ok

jimthompson5910 (jim_thompson5910):

ok have a look at this PDF specifically, look on page 2 http://www.charleston.k12.il.us/cms/Teachers/math/PreAlgebra/paunit8/L8-1.PDF tell me what you think and if it helps you at all. If not, then we can try another way

OpenStudy (anonymous):

It didnt really help me

jimthompson5910 (jim_thompson5910):

ok we start off with a^2 + b^2 = c^2 we're given this

jimthompson5910 (jim_thompson5910):

we want to prove that if that is true, then the triangle has to be a right triangle

jimthompson5910 (jim_thompson5910):

so say we have this triangle |dw:1407470713158:dw|

jimthompson5910 (jim_thompson5910):

let's also say we had another right triangle with legs a and b the right triangle will have a hypotenuse of n |dw:1407470749601:dw|

jimthompson5910 (jim_thompson5910):

by the pythagorean theorem, we can say a^2 + b^2 = n^2

jimthompson5910 (jim_thompson5910):

we're given a^2 + b^2 = c^2 we just found that a^2 + b^2 = n^2 those two left sides are the same, that means c^2 = n^2 take the square root of both sides to get c = n

jimthompson5910 (jim_thompson5910):

so that proves the triangle on the left *has* to be a right triangle for a^2 + b^2 = c^2 to be true

OpenStudy (anonymous):

So like how do I put that into words since I cant use pictures

jimthompson5910 (jim_thompson5910):

you'll just have to describe the pictures. So say something like "start with any general triangle with sides a,b,c." or "we'll have the right triangle with legs a & b with hypotenuse n"

OpenStudy (anonymous):

ok then what

jimthompson5910 (jim_thompson5910):

what do you have so far?

OpenStudy (anonymous):

we'll have the right triangle with legs a & b with hypotenuse n"

jimthompson5910 (jim_thompson5910):

then you can add on something like "by the pythagorean theorem, we can say that a^2 + b^2 = n^2"

jimthompson5910 (jim_thompson5910):

also before all that, you should have statements that declare what you're given, which is: a^2 + b^2 = c^2

OpenStudy (anonymous):

ok now what

jimthompson5910 (jim_thompson5910):

then by substitution, we can say that because a^2 + b^2 = n^2 and a^2 + b^2 = c^2, we know that c^2 = n^2

jimthompson5910 (jim_thompson5910):

then the square root property of equality then allows us to get to c = n

jimthompson5910 (jim_thompson5910):

so effectively, a^2 + b^2 = c^2 is the exact same as a^2 + b^2 = n^2. Because the triangle with side n is a right triangle, that forces the triangle with a,b,c to also be a right triangle

OpenStudy (anonymous):

thank you so much!

jimthompson5910 (jim_thompson5910):

you're welcome

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