# Hl

• Apr 18th 2005, 08:05 PM
mattballer082
HL hypotenuse leg
im having trouble with the HL postulate.. how do you know when you have a leg? and how do you know when to use HL and not to get it mixed up with sss asa aas and sas? is the hypotenuse opposite from the 90 degree angle? what about cpctc?
• Apr 19th 2005, 03:27 AM
ticbol
What does "HL" mean? Hi-lo?

You know what, if you are the only one who can understand your question then you are the only one who can answer or solve it.
• Apr 20th 2005, 12:38 AM
beepnoodle
If you have a right triangle, the side opposite the right angle is called the hypotenuse and the other two are called the legs. The Hypotenuse leg congruence theorem only applies if both of the triangles are right triangles. Basically, if you have two right triangles and they both have the same hypotenuse and the same leg, then the other leg must be the same as well. The other ones, SAS,SSS,ASA,SAA apply to any kind of triangle. Remember, only use HL on RIGHT triangles.
• Apr 21st 2005, 07:01 AM
HallsofIvy
Quote:

Originally Posted by ticbol
What does "HL" mean? Hi-lo?

You know what, if you are the only one who can understand your question then you are the only one who can answer or solve it.

True. However, since "HL" is a common notation in geometry (as are "SSS", "SAS", etc.) and he posted this in the geometry forum, he has every right to assume that anyone responding will understand it. Suggestion: if you don't understand a question simply don't respond at all!

"HL" stands for "hypotenuse, leg". It only applies to RIGHT triangles (which are the only triangles that HAVE legs or hypotenuse!) unlike SSS, SAS, etc. The hypotenuse is always the longest side in a right triangle. If you are not given all lengths, the only way you can be certain that you have a hypotenuse and leg is if you are told that in the problem. Actually, since in a right triangle, all sides are related by the Pythagorean theorem, knowing any two sides give you the third: both "HL" and "LL" are equivalent to "SSS".

You shouldn't have any problem confusing HL with "ASA" because that requires that you know two angles! You shouldn't have any problem confusing HL with "SAS" (there is no "AAS") because those require that the angle be between the two sides- knowing that the triangle is a right triangle is the same as knowing one angle but it is not BETWEEN the leg and hypotenuse (the right angle is opposite the hypotenuse).

"HH" is, in fact, exactly the same as "SAS".
• Apr 21st 2005, 10:34 AM
ticbol
To HallsofIvy
If HL is a common notation in Geometry, how come I don't know it?
Umm, maybe it was introduced lately.

What about his cpctc, do you understand it also?
If yes, why did you not give comment/answer on it?
• Apr 21st 2005, 01:43 PM
mattballer082
cpctc means: corresponding parts of congurent triangles are congurent. thats what i was taught. well i still have a question about HL, will the answer always be HL if its a right angle? or can i use a diffrent answer?
• Apr 24th 2005, 12:12 AM
theprof
Quote:

Originally Posted by ticbol
If HL is a common notation in Geometry, how come I don't know it?
Umm, maybe it was introduced lately.

What about his cpctc, do you understand it also?
If yes, why did you not give comment/answer on it?

I don't think that users of the United States really want to keep out other country users.
Conventions are OK if they are shared
If I say:
Please find the first KLH in the set Y that slorks up and down in ZTL metric without mishkining the HTG
I will for sure be ignored!

BTW, it's the first time in my career I hear the convention you are talking about.
After all we foreigner make the effort to write and read your language... you could kindly make the little effort to write down the problems in a clear way :)

PS
Even if I teach Math in Italian high schools since 1982, I'd never understood that cpctc means corresponding parts of congruent triangles are congruent
• Apr 24th 2005, 12:57 AM
Math Help
I agree totaly agree with the prof. We are an international community here so let us try to be as clear as possible when explaining problems.