# intersction of A sequence of parallel lines and q(x)

jojoba26 shared this question 11 years ago

My GeoGebra version

GeoGebra 3.2.25.0(Java 1.6.0_11,508MB)

August11.2009

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m(x)=4 - sqrt(16 - (x - 4)²)

n(x)=4 - sqrt(16 - x²)

q(x)=If[x < 2, m(x), n(x)]

A2: A set of points with equal distance

B2: A set of parallel lines

I want to draw a sequence of intersections of B2 and q(x)......(as the picture2)

I type the command:sequence[Intersect[q(x), Element[B2, i]],i,1,r]

but it does't work .

would you help me. :confused:

https://ggbm.at/541071 1

Hi

use arcs instead conditional functions ...

https://ggbm.at/541073 1

I think q(x) is a condition fucntion combining two square root functions. and the intersect command does't support it.

--------------------------------------------GeoGebra Help 3.2

Intersect

Intersect[Line g, Line h]: Yields the intersection point of lines g and h.

Intersect[Line, Conic]: Yields all intersection points of the line and conic section (max. 2).

Intersect[Line, Conic, Number n]: Yields the nth intersection point of the line and the conic section.

Intersect[Conic c1, Conic c2]: Yields all intersection points of conic sections c1 and c2 (max. 4).

Intersect[Conic c1, Conic c2, Number n]: Yields the nth intersection point of conic sections c1 and c2.

Intersect[Polynomial f1, Polynomial f2]: Yields all intersection points of polynomials f1 and f2.

Intersect[Polynomial f1, Polynomial f2, Number n]: Yields the nth intersection point of polynomials f1 and f2.

Intersect[Polynomial, Line]: Yields all intersection points of the polynomial and the line.

Intersect[Polynomial, Line, Number n]: Yields the nth intersection point of the polynomial and the line.

Intersect[Function f, Function g, Point A]: Calculates the intersection point of functions f and g by using Newton's method with initial point A.

Intersect[Function, Line, Point A]: Calculates the intersection point of the function and the line by using Newton's method with initial point A. 1

Hi,

The problem is not with Intersect and q(x). The Intersect command works fine with q(x) and an individual element of B2, e.g

Intersect[q,Element[B2,1]] and also see the points K, L, M and N in the attached file.

The problem seems to be with the combination of Sequence and Intersect commands.

I tried Sequence[Intersect[p,Element[B2,i],1],i,1,r]

but all it did was to shift the error message from "unknown command intersect" to "unknown command sequence"

Maybe you should send it to bug reports!

Michael

https://ggbm.at/541081 1

Hi,

I think it may be that you do not have a starting point for the iteration:

Intersect[Function, Line, Point A]: Calculates the intersection point of the function and the line by using Newton's method with initial point A.

Sequence[Intersect[p, Element[B2, i], J], i, 1, r] seems to work OK (for half the curve!)... it works for both sections if δ = 0 ...

I'll see if I can work out the other section!

Sequence[Intersect[p, Element[B2, i], I], i, 1, r] for the other half - needed a different initial point!

Now to see if I can get this to work for the intersections of two polar functions, that I have been struggling with!

Kathryn