Getting a rhombus vertex from one vertex and its area

[Telemachus]

Hi there. I am tryin to solve this one, I know that if I find the way to get one more vertex i'd have it solved.

Homework Statement

The point A(-1,8) is the vertex of a rhombus which minor diagonal is situated on the line L: L=\begin{Bmatrix} x=3\mu &amp; \mbox{ }&amp; \\y=1+4\mu &amp; \mbox{}&amp;\end{matrix}<br />, \mu\in{R}. Get the coordinates of the rest of the vertex knowing that the rhombus area is 30.

Homework Equations

A=\displaystyle\frac{dD}{2}

The Attempt at a Solution

Well, I haven't done too much. Actually I did some, but then I realized that I had confused something, cause I got the line L' where would be located the major D, but I've used for it the point A, and then I was trying to get the point of intersection between L and L', so then I doubled it, and I was going to get my second vertex, but then I realized that it was wrong, cause I couln't use point A, cause A don't belongs to L', it belongs to L, so...

30=\displaystyle\frac{dD}{2}\Rightarrow{60=dD}

So, I don't know much about L', but that its perpendicular to L.

L&#039;=\begin{Bmatrix} x=x_0+4/3\lambda &amp; \mbox{ }&amp; \\y=y_0-\lambda &amp; \mbox{}&amp;\end{matrix}<br />

 

[tiny-tim]

Hi Telemachus!

So, I don't know much about L', but that its perpendicular to L.

That's right , but from then on you're making it too complicated.

Hint: Where is the midpoint of the rhombus? ​

 

[Telemachus]

On the intersection between L and L', but how should I get L'? I thought maybe using pythagoric equation I could find another vertex, but I am not too sure. I know it gives enough data, but I don't know how to use it.

 

[Telemachus]

I had a misunderstood, I think I was on the right way, cause actually I didn't corroborate if A belongs to L, and the sentence don't say so. I'll corroborate, if it doesn't I was on the right way, and it will be easy to solve, cause if A don't belongs to L, it must belongs to L'.

Bye there, and thanks.

 

[tiny-tim]

On the intersection between L and L', but how should I get L'?

L' is perpendicular to L, and goes through A.

(and remember, you don't need to find L', you only need the midpoint )

 

[Telemachus]

How could I get the midpoint without L'? I thought of it as the intersection between L and L'.

 

[tiny-tim]

AM is on L', so it's perpendicular to L.