Geometry proof (1 Viewer)

[kurt.physics]

I just have this one question that i cant do, it is;

Q1) In the diagram (attached), KJ//MN, prove that angle KLM is a right angle.

 

[namburger]

I just have this one question that i cant do, it is;

Q1) In the diagram (attached), KJ//MN, prove that angle KLM is a right angle.

What are the conditions for the point L

 

[kurt.physics]

What are the conditions for the point L

Doesnt say, the whole question reads as i have written in the first post, thats all what was given. Mind you, this is in a year 10 textbook! I gave it to my teacher and after 30 minutes of thinking she couldnt do it! So it must be hard.

I made a line parallel to JK and MN that goes through L. But i can seam to prove it.

 

[ronnknee]

Mm I looked at your profile and it says you're only 14 years old?
Is this question really suitable to be in the 4U forum?

 

[undalay]

As stupid as this sounds.

Get a potracter and measure it.

In sc they allow measurement to find angles.
Solving by any other means is impossible without more information.

 

[Mark576]

This question is literally impossible. Don't bother trying to prove it. There is no restriction on L, and so it's like trying to prove that ∠KLM is a right angle wherever we place L, since L can be moved anywhere. That obviously is impossible.

 

[kurt.physics]

It asks me to prove it, so i dont think using a protractor will be acceptible. Its in the text, so im thinking that it should be able to prove?

Ronnkne have you finnished?

... Is this question really suitable to be in the 4U forum?

Must be if you 4 uniters are finding it hard!
http://community.boredofstudies.org/member.php?u=139637 <script type="text/javascript">vbmenu_register("postmenu_3477332", true); </script> <!-- Added by James for Benefactors: 11.30pm, 8 Feb 2005 -->
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[undalay]

Must be if you 4 uniters are finding it hard! <!-- Added by James for Benefactors: 11.30pm, 8 Feb 2005 -->
<!-- Added by James for BigBloggers: 18 April 2006 -->

It's not "hard". It's just a broken question, with that little information, the only way is to measure it physically.


It's like asking; prove x = 1 when y = 2, without any given relationship between x and y.

edit: You could measure the sides, and prove that pythagoras works (hence it must be a right angle)
But once again, you'll be measuring stuff.

 

[ronnknee]

Actually I take back what I said about coming up with the proof
I thought I did with co-interior angles
But after some thinking
It is impossible to prove algebraically without any given conditions
As L can be moved around and the angle would vary

Consider this

Since there's no restriction on L
L₁ and L₂ are possible positions of L
It is clear that the angles KL₁M and KL₂M are different
And NOT definitely 90 degrees ALL the times
So therefore, the protractor method sounds plausible in this case

Don't have the misconception that because we're 4U we can do every question
If the question itself is flawed, no matter how much time we spend on it, we still won't get the answer

 

[namburger]

Proof:
By inspection, it looks like a right angle

 

[tommykins]

haha I lol'd.

But unless a given condition is placed upon the point L, it is impossible to determine.

 

[kurt.physics]

...that because we're 4U we can do every question
If the question itself is flawed, no matter how much time we spend on it, we still won't get the answer

I believed the question was flawed, but what am i suposed to write as the answer?

 

[ronnknee]

Well if you must show working
Then the method that undalay suggested would be a good idea
Construct LM and LK so that it is a triangle
Measure their lengths
If LM² + LK² = MK²
Then the triangle must be right angled since Pythagoras theorem applies

 

[kurt.physics]

I calculated that, through pythagoras theorem, the hypotenuse should be roughly 7. It is 3.5! So i conclude that the diagram is not to size.

What do i wright?

 

[ronnknee]

Where did you get this question from specifically?
If that method and the protractor method don't work
Then I don't know

 

[kurt.physics]

Where did you get this question from specifically?
If that method and the protractor method don't work
Then I don't know

Unfortunately im doing year 10 math through distance education, i would be doing year 11, but thats another story. It comes from the year 10 5.3 Maths title page book they have given me.

 

[undalay]

books wrong.

If the only information given is the diagram and;

If pythagoras doesn't work, then obviously the angle is not 90 degrees.

or theres like extra info in invisible ink

 

[Poad]

I calculated that, through pythagoras theorem, the hypotenuse should be roughly 7. It is 3.5! So i conclude that the diagram is not to size.

What do i write?

Put a line through it and move on?

 

[mick135]

I calculated that, through pythagoras theorem, the hypotenuse should be roughly 7. It is 3.5! So i conclude that the diagram is not to size.

What do i wright?

haha - gotta love his ability to spell

yeah - protactor is the best way to go
could be a smarty pants and use the pythag thing but not much point to the question

 

[Affinity]

You must have left something out... for example something along the lines of NML JKL add up to 90