Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

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

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

Offline

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

use the pythagorean formula (a² = b² + c²)

a= hypotonuse

b= side

c= side

therefore

26² = 10² + x²

676 = 100 + x²

x² = 576

x = 24

Offline

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

thanks alot man

Offline

**KatiePM****Guest**

dude thanks!!!u helped me too

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

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.

Offline

**Sunnayyy****Guest**

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

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

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.

Offline

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

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)*

Offline

**sammy8cindy****Guest**

:(: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

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

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

Offline

**John E. Franklin****Member**- Registered: 2005-08-29
- Posts: 3,588

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**

Offline

**tareena****Guest**

what if there is a non right traingle

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

Well, then you need trigonometry.

Linux FTW

Offline

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 21,477

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

It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

Offline

**John E. Franklin****Member**- Registered: 2005-08-29
- Posts: 3,588

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**

Offline

**just myself****Guest**

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

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

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.

Offline

**Veronica Vazquez****Guest**

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

**careless25****Real Member**- Registered: 2008-07-24
- Posts: 559

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

Offline

**ppoooopp****Guest**

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?

**ppoooopp****Guest**

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

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

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.

Offline

**mastercatt****Guest**

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

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

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.

Offline

**professor ralph****Guest**

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.