# points of intersection along curve and horizontal line [duplicate]

I'm trying to find the intersection points of the following plot with the given boundaries. How would I do so in the bounds set by the above plot? I've tried FindRoot by setting the lines equal to each other and doing {t,0} but my program won't load in a result.

Plot[{(2000/
5280 E^(-1.21 ((2.5 + 1.5 Cos[Pi/3 t] - 1)^2 + (2.4 +
1.1 Sin[Pi/3 t] - 3.5)^2))) + (2000/
5280 E^(-4 ((2.5 + 1.5 Cos[Pi/3 t] - 4.5)^2 + (2.4 +
1.1 Sin[Pi/3 t] - 1.5)^2))) + (-950/
5280 E^(-1 ((2.5 + 1.5 Cos[Pi/3 t] - 2.8)^2 + (2.4 +
1.1 Sin[Pi/3 t] - 3.7)^2))) + (1000/(
5280 (1 +
2.25 ((2.5 + 1.5 Cos[Pi/3 t] - 2.5)^2 + (2.4 +
1.1 Sin[Pi/3 t] - 1.8)^2)))) + (1500/(
5280 (1 +
1.21 ((2.5 + 1.5 Cos[Pi/3 t] - 3)^2 + (2.4 + 1.1 Sin[Pi/3 t] -
2)^2)))) + (3500/(
5280 Sqrt[
1 + 3.61 ((2.5 + 1.5 Cos[Pi/3 t] - 1)^2 + (2.4 +
1.1 Sin[Pi/3 t] - 1)^2)])) + (2000/(
5280 Sqrt[
1 + 4 ((2.5 + 1.5 Cos[Pi/3 t] - 4.25)^2 + (2.4 +
1.1 Sin[Pi/3 t] - 4.1)^2)])) + (200/5280 Sqrt[
1 + .25 ((2.5 + 1.5 Cos[Pi/3 t] - 2.75)^2 + (2.4 +
1.1 Sin[Pi/3 t] - 3.75)^2)]) + 7000/5280, 1.893939}, {t, 0, 6}]

• The methods in the linked question are all usable for your specific case. – J. M.'s torpor Nov 15 '19 at 2:59

expr = (2000/
5280 E^(-1.21 ((2.5 + 1.5 Cos[Pi/3 t] - 1)^2 + (2.4 +
1.1 Sin[Pi/3 t] - 3.5)^2))) + (2000/
5280 E^(-4 ((2.5 + 1.5 Cos[Pi/3 t] - 4.5)^2 + (2.4 +
1.1 Sin[Pi/3 t] - 1.5)^2))) + (-950/
5280 E^(-1 ((2.5 + 1.5 Cos[Pi/3 t] - 2.8)^2 + (2.4 +
1.1 Sin[Pi/3 t] - 3.7)^2))) + (1000/(5280 (1 +
2.25 ((2.5 + 1.5 Cos[Pi/3 t] - 2.5)^2 + (2.4 +
1.1 Sin[Pi/3 t] - 1.8)^2)))) + (1500/(5280 (1 +
1.21 ((2.5 + 1.5 Cos[Pi/3 t] - 3)^2 + (2.4 +
1.1 Sin[Pi/3 t] - 2)^2)))) + (3500/(5280 Sqrt[
1 + 3.61 ((2.5 + 1.5 Cos[Pi/3 t] - 1)^2 + (2.4 +
1.1 Sin[Pi/3 t] - 1)^2)])) + (2000/(5280 Sqrt[
1 + 4 ((2.5 + 1.5 Cos[Pi/3 t] - 4.25)^2 + (2.4 +
1.1 Sin[Pi/3 t] - 4.1)^2)])) + (200/5280 Sqrt[
1 + .25 ((2.5 + 1.5 Cos[Pi/3 t] - 2.75)^2 + (2.4 +
1.1 Sin[Pi/3 t] - 3.75)^2)]) + 7000/5280

roots = NSolve[expr == 1.893939 && 0 < t < 6, t]


gives roots:

{{t -> 2.20967}, {t -> 2.63666}, {t -> 3.52713}, {t -> 4.85185}}

And we can visualize them:

Plot[expr, {t, 0, 6}, Frame -> True, Mesh -> {{1.893939}},
MeshFunctions -> (#2 &),
MeshStyle -> Directive[PointSize[Medium], Red],
GridLines -> {t /. roots, {1.893939}},
GridLinesStyle -> {Directive[Gray, Dashed],
Directive[Thick, ColorData]}] • Thank you so much! – Elijah Shepherd Nov 15 '19 at 2:11
• You are welcome! – Alx Nov 15 '19 at 2:47