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#1 2006-05-24 09:06:56

bryan
Member
Registered: 2006-05-24
Posts: 4

finding the missing side of a triangle

i have a triangle it is a right triangle
the hypotonuse is 26
one leg is 10
the other leg is X
i do not know what to do to slove for x

        l
        l  =
        l    =
        l       =      26
    10 l          =
        l            =
        l               =
        l_                 =                                                     
        l_l___________=
             X


that is the best way i could stech it on thereso do not hate

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#2 2006-05-24 09:38:43

3daniel
Member
Registered: 2006-05-24
Posts: 3

Re: finding the missing side of a triangle

use the pythagorean formula (a² = b² + c²)
a= hypotonuse
b= side
c= side
therefore
26² = 10² + x²
676 = 100 + x²
x² = 576
x = 24

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#3 2006-05-24 09:40:25

bryan
Member
Registered: 2006-05-24
Posts: 4

Re: finding the missing side of a triangle

thanks alot man

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#4 2007-04-30 11:14:44

KatiePM
Guest

Re: finding the missing side of a triangle

dude thanks!!!u helped me tooup

#5 2007-04-30 11:40:36

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

Re: finding the missing side of a triangle

If you're well-versed in Pythagorean triples, you could also recognise that as double the 5-12-13 triangle, which would help you find the answer quicker. Otherwise, 3daniel's method is perfectly good as well.


Why did the vector cross the road?
It wanted to be normal.

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#6 2008-02-06 04:04:34

Sunnayyy
Guest

Re: finding the missing side of a triangle

i need help figuring out how to find the missing side of a right triangle with legs: a= 12, and b=9....?

#7 2008-02-06 04:36:21

Daniel123
Member
Registered: 2007-05-23
Posts: 663

Re: finding the missing side of a triangle

In every right-angled triangle, the sum of the squares of the two shorter sides is equal to the square of the longer side. In other words, to find the length of the longest side, you square the other two sides, add them together, and then square root. ie:

a² = b² + c² where a is the longest side.

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#8 2008-02-06 06:06:03

LuisRodg
Real Member
Registered: 2007-10-23
Posts: 322

Re: finding the missing side of a triangle

Sunnayyy wrote:

i need help figuring out how to find the missing side of a right triangle with legs: a= 12, and b=9....?

So by following the formula given before:

Where:

a and b are the sides and c is the hypotenuse.

So you have sides a=12 and b=9.





Last edited by LuisRodg (2008-02-06 06:07:35)

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#9 2008-03-31 09:46:47

sammy8cindy
Guest

Re: finding the missing side of a triangle

shamedownsweardunno:(:mad:this didn't help me at all!!!!

3daniel wrote:

use the pythagorean formula (a² = b² + c²)
a= hypotonuse
b= side
c= side
therefore
26² = 10² + x²
676 = 100 + x²
x² = 576
x = 24

#10 2008-03-31 10:14:44

LuisRodg
Real Member
Registered: 2007-10-23
Posts: 322

Re: finding the missing side of a triangle

Why didnt it help you? Its perfectly clear. I think the problem lies on the other side of the screen.

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#11 2008-03-31 13:04:26

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,562

Re: finding the missing side of a triangle

Here's another one to help you.
The big side is 5 long.
The short side is 3 long.
The medium side is 4 long.
The angle between the
two short sides must be
like a square corner to do
it this way.
         l
         l  =
         l    =
         l       =     5×5=25
  4     l          =
×4     l            =
___    l               =
16     l_                 =                  Here's the cool part!! 25 - 16 = 9                                       
         l_l___________=                   and 25 - 9 = 16   
               3×3=9                               and  9 + 16 = 25


igloo myrtilles fourmis

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#12 2008-05-24 11:38:32

tareena
Guest

Re: finding the missing side of a triangle

what if there is a non right traingle

#13 2008-05-24 11:57:55

simron
Real Member
Registered: 2006-10-07
Posts: 237

Re: finding the missing side of a triangle

Well, then you need trigonometry.


Linux FTW

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#14 2008-05-24 17:51:29

ganesh
Moderator
Registered: 2005-06-28
Posts: 13,819

Re: finding the missing side of a triangle

tareena wrote:

what if there is a non right traingle

If a triangle is not a right angled triangle (or simply right triangle), it is not possible to find the length of the third side when two sides are given. However, if the included angle is known, or if all the three angles are known, the length of the third side can be calculated.

As simron said, you need to know trignometry.

The law of sines states that

where a,b, and c are the sides and A, B, and C are the angles.

The law of cosines states that


Character is who you are when no one is looking.

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#15 2008-05-25 03:55:58

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,562

Re: finding the missing side of a triangle

The cosine law ganesh said is complicated but
really neat.  Notice if the biggest angle in the
triangle gets really big, like as wide as possible
like 178 degrees or something.  180 degrees is
just a straight line, you know?  Really, 180
degrees is not a turn at all, unless you are
walking along and then turn around, but that
is different.  We are walking along, and then
we turn around and don't count that one, and
then we turn around again and count that
one as 180 degrees, so 180 degrees ends up
being a straight line.  Kind of hard to explain
with just words.  But anyway the 2xyCosZ stuff
ganesh said is cool when the angle gets really
large between 91 and 179 degrees or so.
Why?  Well the opposite side gets really
long.  That sort-of-hypotenuse is bigger than
the hypotenuse in a right triangle!!  And the
"minus 2bcCosA" stuff become POSitively
a Plus sign and makes the other side
longer!!  Isn't that awesome!!  When you
learn cosines, you will see that they can
change the sign to + or - and this is very
powerful!!


igloo myrtilles fourmis

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#16 2008-12-14 10:26:16

just myself
Guest

Re: finding the missing side of a triangle

im so confused okay so i have a triangle with a side of 23 and 9 whats the missing side length

#17 2008-12-14 11:30:48

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

Re: finding the missing side of a triangle

With just that information, you can't tell. The missing side could be anything between 14 and 32.
You can do it if you also have the angle between the two known sides though.


Why did the vector cross the road?
It wanted to be normal.

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#18 2008-12-15 10:42:10

Veronica Vazquez
Guest

Re: finding the missing side of a triangle

is there enyone on right now i really need help like ASAP  im completely lost i really dont understand math someone please help ne!!!!!!!

#19 2008-12-15 10:47:19

careless25
Real Member
Registered: 2008-07-24
Posts: 555

Re: finding the missing side of a triangle

Post your question n i will see if i can help. wink

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#20 2008-12-17 12:39:36

ppoooopp
Guest

Re: finding the missing side of a triangle

i remember doing this in school but now it doesnt seem to want to work.  I have a right triangle and its hypotenuse is 3 and height is 2 how does that not work?

#21 2008-12-17 13:33:35

ppoooopp
Guest

Re: finding the missing side of a triangle

okayokayokay sorry i was doing a question where pythagorean theorum doesnt apply apparently because you have to find the area of a triangle and it has a missing side and pythag has nothing to do with it guess theres another way to find the side

#22 2008-12-17 13:51:15

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

Re: finding the missing side of a triangle

Pythagoras could apply to that, if it's the same triangle as in your first post.
If the hypotenuse is 3 and the height is 2, then the base length is √(3²-2²) = √5.

You now know the base and height of the triangle, so you can use the A = 1/2 bh formula to find the area.

A = 1/2 * 2 * √5 = √5.


Why did the vector cross the road?
It wanted to be normal.

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#23 2008-12-22 04:13:32

mastercatt
Guest

Re: finding the missing side of a triangle

whatThis didn't help me...i need to know how to find any side with only one side on a 30-60-90 triangledunno

#24 2008-12-22 05:47:48

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

Re: finding the missing side of a triangle

On a 30-60-90 triangle, the longest side is always twice as big as the shortest side.
That fact, along with Pythagoras and the side length you know, should let you find out everything about the triangle.


Why did the vector cross the road?
It wanted to be normal.

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#25 2008-12-22 05:55:43

professor ralph
Guest

Re: finding the missing side of a triangle

To find the any side of a triangle knowing all the angles of said triangle and one side use the law of sines.  Say the known side is side "A"  and using the angle opposite it as angle A find its sine (i.e. sine(A)).  Now set up a proportion:
        [sine (A)] ÷ A   =   [sine (B)] ÷ B
where B is the side sought and sine(B) refers to the sine of the angle opposite side B.

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