# Intersection with list of conics - bug?

Angsüsser shared this problem 2 months ago
Not a Problem

Intersection with a list of conics (hyperbolas in my case) only shows 1 intersection point:

1) hyp:x^2-y^2=1 /* hyperbola */

2) x_s:0.5*x /* line */

3) Intersect(x_s, hyp) /* provides 2 intersection points - fine!*/

4) hypList:Sequence(x^2-y^2=n^2, n, 2, 3)

5) Sequence(Intersect(x_s, Element(hypList, k)),k,1,2)

Only shows 1 intersection point - as you can see in the attached file!

The only ugly work around I know is another Sequence with indexed intersection points and flatten the list afterwards.

Why is an element of a list of hyperbolas treated not the same way as a single hyperbola? 1

Does this help?

```5) Sequence({Intersect(x_s, Element(hypList, k))},k,1,2)

``` 1

(maybe with Flatten() too) 1

Place Intersect() inside this Sequence() in curly brackets -> {Intersect()}

l1 = Flatten(Sequence({Intersect(x_s, Element(hypList, k))}, k, 1, 2))

2 elements must be created per index k. This requires the curly brackets, so that only 1 expression (a list) is created inside the Sequence(). This is then dissolved using Flatten().

---------------

Sorry, time overlap with Michael Borcherds. 1

Curly brackets are the solution - no chance to see this without your help!

Thank you Michael, thank you rami

Problem solved!