There are two ways to do this cache: the Easy Way and the Hard Way. The cache is, as required, within 2 miles of the posted location. The posted coordinates are the recommended parking.
The Easy Way: Complete Two Adventure Labs
To get the coordinates for this cache, complete both the "Got a Clue?" AND "Not a Clue!" Adventure Labs in Cook Park. Although you can do either Adventure Lab in any order, the fastest way is to do both labs simultaneously, switching back and forth between them as you encounter waypoints. These two labs will take you on a tour of Cook Park as you play a virtual version of the old board game, "Clue." Your mission is to solve the crime: who did it, with what weapon, and where.
The 6 suspects are Mr. Green, Col. Mustard, Mrs. Peacock, Professor Plum, Miss Scarlet, and Mrs. White.
The 6 possible weapons are a Candlestick, Knife, Lead Pipe, Revolver, Rope, and Wrench.
The 9 possible locations are the Ballroom, Billiard Room, Conservatory, Dining Room, Hall, Kitchen, Library, Lounge, and Study.
Upon successful completion of the question at each waypoint, a detective will show you one or two cards that you can eliminate from suspicion, or provide other useful information. Once you have seen 18 cards, you will be able to determine the 3 cards you haven't seen, which represent the guilty party, the weapon, and the room. Enter the three pieces of information into the certitude checker as described in the Adventure Lab to obtain the coordinates for this bonus cache.
You can validate your puzzle solution with certitude.
The Hard Way: Moriarty Method
Moriarty is a criminal mastermind who had this vow related to Sherlock Holmes: "if you are clever enough to bring destruction upon me, rest assured that I shall do as much to you." Moriarty was a mathematician, hence the use of math in the "Moriarty Method" to get the coordinates for this cache without doing the Adventure Lab. As a mathematician, Moriarty strictly follows order of operation with his equations. There are consequences to using the Moriarty method: you will probably need to do more walking, you will need to do more calculation, you will not have a way to validate your solution, and you will not have any hints to find the cache. On the other hand, you will avoid doing the adventure labs and will not receive credit for the 10 finds they represent. The choice is yours.
To use the Moriarty Method, explore Cook Park on your own to gather the information listed below, in no particular order, which you can use to solve for X and Y. Moriarty has not provided you the locations for any of these locations, but has restrained himself to using locations that are within the boundaries of Cook Park, including the paths to the west as far as 108th that some maps do not include as part of the park. You do not need to go into Durham or Tualatin parks.
Let a = J. Dolan's Troop number
Let b = the year of Harlow Rock
Let c = the milepost number near water quality station #024
Let d = D. M. Lett's age, in days
Let e = C.P. Luby's age, in days
Let f = the age Ruth G was on her birthday the year Ruth L was born
Let ghi = the 3-digit number of Ryan L's troop
Let j = total number of eyes (open and closed) on all of the stone vertebrates in all of the park playgrounds
Let k = numeric value of G.F.L., Sr's birth month
Let m = numeric value of month of Justin's bench
Let n = numeric value of month of James' bridge
Let p = numeric value of month of Frank's bench
Let q = distance to Cook Park at the 1.2 milepost sign
Let r = date of the high water mark (mmddyyyy)
Let s = checksum of F.T.D.'s troop
Let t = checksum of Mr. Lewis' birth year
Calculate α = (a*b)^c. Round to the nearest whole number
Calculate β = d*e
Calculate γ = α-β
Let δ = the reverse digits of γ. For example, if γ=123 then δ=321.
Reverse the center 2 digits of δ.
Calculate ε = δ/f
Calculate ζ = h*100+((h+i)*10)+j
Calculate η = ε+ζ
Calculate θ= g*10^g+i*10^i
Calculate ι = η - θ-k^(j+n)
Calculate κ = ((j*k*m*p)^n)*q
Calculate λ = n*(κ-r)
Calculate μ = ((s-n)*10^f)+(n*k^j)+(t*k+s)
Calculate ν = (λ+μ)^(f-j)
If you've saved all of the calculations, two of the numbers will be especially interesting.
You can validate your puzzle solution with certitude.