Can someone explain how the 40th maximum and minimum are worked out on a graph? Sombody told me to do this. But i'm having a hard time understanding this. Thanks

find the first point & write it down.
figure out how far apart the points fitting the criteria are (how far it is from the first point wanted to the second, second to third, etc)
write down the first point & then what needs to be added to it to get the next couple of points, in terms of the first point & the distance apart.
----After a few points a pattern should be noticed that makes it easy to figure out.----

B = first point
* = how far apart
T = wanted term

1. B
2. B+*
3. B+2*

1. B+0*
2. B+1*
3. B+2*...
T. ???