Answer:
9.8
Step-by-step explanation:
Use the distance formula to determine the distance between the two points.

d = distance
= coordinates of the first point
= coordinates of the second point

via the angle sum identity for cosine.
We're comparing 80,000 with 80.
One way to do this is divide the two numbers: 80,000/80 = 1000.
80,000 is one thousand times greater than 80.
(a) The team captain wants to know what his teammates eats before a match
Team captain know by taking a survey of teammates
(b) The team captain wants to know who can score most goals against the best player
This can be known by observation of games. so its observational study
(c) The team captain wants to know how praising the affects the teammates performance.
This can be known by experiment
(d) The team captain wants to know what other sports teammates play
This can be known by observation of games. so its observational study
Answer:
No solution
Step-by-step explanation:
We have

For the sum it is not correct to assume

Note that for

it is assumed
and in your case
for 
In fact, considering a set
we have
that satisfy 
This means that, by definition 
Therefore,

because the sum is empty.
For

we have other problems. Actually, this case is really bad.
Note that
has no value. In fact, if we consider for the case
, the cosine function oscillates between
, and therefore it is undefined. Thus, we cannot evaluate

and then

has no solution