Answers
There are many possible positions of . However, for a participant to be considered as winner, they must have submitted at least one correct posiiton of
.
The easiest to get is (-4,10). Nevertheless, any participant who submitted any possible position of in the original problem shall be considered as winner.
Solutions
Graphing method
We can visually obtain the position of is to draw the points, and draw circles around
with radius starting from 1 and increasing by 1, and
with starting radius 2 and increasing by 2, until the circumferences of the circles touch each other at least once above 6 in the y-axis.
(12, 6.032) is a possible position of based on the graph, though you have to use a big and precise graphing area (graphing apps such as Desmos is recommended).
Distance between A and H
= sqrt((10 - 12)^2 + (2 - 6.032)^2)
= sqrt((-2)^2 + (-4.032)^2)
= 4.5008
Distance between A and J
= sqrt((3 - 12)^2 + (6 - 6.032)^2)
= sqrt((-9)^2 + (0.032)^2)
= 9.0001
Because we used approximation in 6.032, we get rounding error in the distances. However, that is an acceptable error.
Midpoint method
Just place somewhere on the graph such that
becomes the midpoint of
and
.
The midpoint formula is (xm, ym) = ((xa + xb)/2, (ya + yb)/2), such that:
- (xm,ym) =
's position which is (3,6)
- (xa, ya) =
's position which is unknown
- (xb, yb) =
's position which is (10,2)
Our equation is now (3,6) = ((xa + 10)/2, (ya + 2)/2). In the equation, xa = -4 and ya = 10. Therefore, a possible position of is (-4,10).
Systemic method
Nevermind the solution below, since I believe I already explained enough using the easier solutions above, unless you want 🤯
This method involves systems of equations.
- Let's use capital letters as positions of the persons. A for
, H for
, and J for
.
- Let (x,y) be the coordinates of
.
Let d be the distance of from
Let 2d be the distance of from
We use the distance formula to get the distance between any two points. The distance formula is
the distance is equal to the square root of the sum of the squares of the difference between the change in y and change in x
Using the distance formula and the two distance equations above, we get the two equations:
- d^2 = (10 - x)^2 + (2 - y)^2
- d^2 = x^2 - 20x + 100 + y^2 - 4y + 4
- Equation 1: d^2 = x^2 - 20x + y^2 - 4y + 104
- (2d)^2 = (3 - x)^2 + (6 - y)^2
- (2d)^2 = x^2 - 6x + 9 + y^2 - 12y + 36
- Equation 2: 4d^2 = x^2 - 6x + y^2 - 12y + 45
Since the d on Equation 1 is the same as d on Equation 2, we can substitute Equation 1 to Equation 2.
- x^2 - 6x + y^2 - 12y + 45 = 4 * (x^2 - 20x + y^2 - 4y + 104)
- x^2 - 6x + y^2 - 12y + 45 = 4x^2 - 80x + 4y^2 - 16y + 416
- 3x^2 - 74x + 3y^2 - 4y + 371 = 0
- x^2 - 74x/3 + y^2 - 4y/3 + 371/3 = 0
- (x^2 - 74x/3 + 1369/9) + (y^2 - 4y/3 + 4/9) + 371/3 - (1369/9 + 4/9) = 0
- (x + 37/3)^2 + (y - 2/3)^2 - 260/3 = 0
- Equation 3: (x + 37/3)^2 + (y - 2/3)^2 = sqrt(260/3)^2
We can use any pair of x and y values satisfying Equation 3 for as long as y is greater than 6. The higher of and
's positions has a y-intercept of 6.
Winner: none 🤯
1 HIVE shall be distributed to the previous winners in proportion to the number of days they correctly answered first.
RE: Math mini-contest problem for Day 2 on D.Buzz