# Intersection doesnt work properly

Nibiru shared this question 7 years ago

So I have f(x) = sin(π x / 2 - 1) + 2 and im trying to get intersection points between g(x)=2, lets say in an interval from 0 to 12. I use command for intersection between two graphs in interval 0,12 and it just doesnt work. Same problem if try to do it manually with the option "Intersection between two objects". It gives me an intersection point in some other place, but not in the position I want.

Must to admit, that it works sometimes, but not often. Im using the latest version for GG 4.2.

1

Does this help?

Roots[sin(π x / 2 - 1) ,0,12]

If not you can try something like:

Intersect[f, g, (1, 2)]

Intersect[f, g, (3, 2)]

etc

1

Thnx for response. Must say that today when i try to use the option "Intersection between two objects" it works totally fine. Strange, why it didnt work before. I just dont wanna get screwed on exam. Your first suggestion just gives me x-coordinates of the intersection points. I could of course make a vertical line, but it will take time. Your second suggestion didnt work for me.

1

Murkle,

I am a new Geogebra user (4.2) - a newbie.

I don't see why Roots[] would work since there is no relation to g(x) in your proposal. Can you explain?

Intersect works great for me - this time. Like Nibiru I don't always get a complete solution - just the first intersection point.

Thanks

Ron

1

I don't always get a complete solution - just the first intersection point.

BTW, I forgot this syntax which is better for the original question:

Intersect[<Function f>, <Function g>, <left-x>, <right-x>]

Calculates the intersection points for the two functions in the given interval.