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 #1
avatar+505 
+3

I know this is a troll question, but here you go :)

 

I am guessing a lot of stuff since you didn't put them in (work distance, etc.) Also, the answer will be a rough estimate in years.

35, 757, 093 minutes to get to the store-----> roughly 697.01 years

 

Since your father is slow in the head, it will take him about 5 minutes to realize he doesn't have enough money to buy the milk. Going to

work, guessing about 30 miles from the store in the opposite direction of your house, it takes him, with the given 0.05 mph, about 600 hours or 0.07 years, to get to his work.

 

 

That is if, and only if, a cop does not pull over your father for the 200th time for diving immensely slow. It would be a usual sentence of fewer than 30 days. However, your father has been there a lot and the judge has had enough of your father being a public nuisance. This makes the judge sentence your father to jail time for 50 years. Worst-case scenario, your father is sentenced to a lifetime jail residence so make that infinite years.

 

However, let's not think that way. He gets to work and has to work for the listed 950, 000 days (roughly 2666.67 years). Getting back to the store will take another 0.07 years, buying the milk will take about 50 more years with the state your father's mind is in. Finally, it will take another 697.01 years to get home. 

 

 

Totaled up, this is an approximate 4160.83 years for your father to come back home with the milk. Unfortunately, the milk is spoiled by the time he gets home, unless it's the special "Never Go Bad Milk" brand, which is probably not the case since your father probably read the label wrong and got the "Goes Bad in 3 Seconds Milk" brand instead. Thus repeating the never-ending cycle.

Jun 1, 2022
 #1
avatar
+2

Hints:

1-Think about the general form of a "Rotation Matrix" (Something to do with cos(theta),sin(theta),-sin(theta),cos(theta), arranged in a 2x2 matrix).

2-A 2x2 matrix that dilates by scale factor of k must have two elements out of the four as "k"  and the other two elements are 0, as it is centered about the origin.

3-BA means multiply matrix A by matrix B, and order matters (B first then A). Use (1) and (2) to find BA.

4-You are given BA, compare each element you got from (3) with the corresponding given element.

5-Look for the desired system of equations.

6-Solve the system (Further hint: Think of tan(theta)=sin(theta)/cos(theta))

7-It seems there exists two answers for theta... Are both valid? Why? Why not?
8-Hint: k is positive! 

 

 

 

 

 

 

Solution:

Ok, if A is a rotation matrix then it must be:

\(A=\begin{bmatrix} cos\theta && -sin\theta \\ sin\theta && cos\theta \end{bmatrix}\)

and If B is a matrix that dilates then it must be: \(\begin{bmatrix} k && 0 \\ 0 && k \end{bmatrix}\)

 

So given: \(BA=\begin{bmatrix} -1 && -1 \\ 1 && -1 \end{bmatrix}\)  \(=\)    \(\begin{bmatrix} k && 0 \\ 0 && k \end{bmatrix}\) * \(\begin{bmatrix} cos\theta && -sin\theta \\ sin\theta && cos\theta \end{bmatrix}\)

\(\begin{bmatrix} kcos\theta && -ksin\theta \\ ksin\theta && kcos\theta \end{bmatrix}\)

and just comparing each element of the matrix yields a system with sufficient equations to find both k and theta.

\(-1=kcos\theta \text{ And, }1=ksin\theta\)

Divide the latter by the former:

\(\frac{ksin\theta}{kcos\theta}=-1 \iff tan\theta=-1\), therefore, \(\theta=135,315\) Now, which one of these is the answer depends on the previous system of equations.

Well, since k is positive, then \(\frac{-1}{cos\theta},\frac{1}{sin\theta}\) must be positive. If \(\theta=135\), this is satisfied. But, If \(\theta=315\) 1/sin(theta) will be negative! Hence k is negative, but we are given k>0. Thus we reject \(\theta=315\).

Therefore, \(\theta=135\) only, yielding: \(k=\sqrt{2}\)

.
Jun 1, 2022
 #1
avatar+118723 
+1
Jun 1, 2022

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