# Thread: Need help with vectos

1. ## Need help with vectos

I thought to find the midpoint of B and the negative y-axis, and then equate the y-coordinate to sqrt(14) but that did not seem to be the way..

2. ## Re: Need help with vectos

Hey Tutu.

(Hint: Try using Pythagoras' Theorem).

3. ## Re: Need help with vectos

But how, I do not know the coordinates of the other end of B?

4. ## Re: Need help with vectos

You know the height of B and you know the hypotenuse.

Use the fact that a^2 + b^2 + c^2 = d^2 where you know d = SQRT(14) and a = -1, b = 2. (I'm using a 3D version of the Pythagoras' Theorem).

5. ## Re: Need help with vectos

Sorry, how did you get a^2 + b^2 + c^2 = d^2 ? And how did you get those values..?
Sorry

6. ## Re: Need help with vectos

This is the form of the distance formula in three dimensions (as opposed to the one in two).

The hypotenuse is given in the question and the rest is found from the values in your diagram.

7. ## Re: Need help with vectos

I just went to search online,

they said a is the left right distance, b is the front back distance and c is the up down distance.
I understand why a^2 + b^2 + c^2 = d^2 but then shouldn't a be -1, b be -1, and c be 2?
How did you know sqrt 14 is the distance? The more I look at the diagram, it looks like the midpoint!

8. ## Re: Need help with vectos

You are right in that a = -1 and b = -1 and you need to find a value of c where d = SQRT(14).

9. ## Re: Need help with vectos

I got c to be sqrt(12)?

10. ## Re: Need help with vectos

That looks right.

11. ## Re: Need help with vectos

But from there, how do I find the two coordinates on the y-axis?
Sorry that I still cannot get this!

12. ## Re: Need help with vectos

Find the y-point +- SQRT(12) of the B's y-point (which is -1 according to the diagram).

13. ## Re: Need help with vectos

So it's -1+sqrt(12) and -1-sqrt(12)?

14. ## Re: Need help with vectos

Yes, that is the idea.

15. ## Re: Need help with vectos

I found the answer sheet, it says the answer is (0,2,0) and (0.-4,0)!

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