Answer:
That would be sina.
Step-by-step explanation:
sin(a+b) = sinacosb + cosasinb
sin(a-b) = sinacosb - cosasinb
Adding we get sin(a+b) + sin(a-b) = 2sinaccosb
so sinacosb = 1/2sin(a+b) + sin(a-b)
For this case we have the following equation:

From here, we must substitute ordered pairs of the form:
(x, y)
If the ordered pair satisfies the equation, then it belongs to the line.
We have then:
For (8, 5):
We substitute the following values:

We observe that the equation is not satisfied and therefore, this point does not belong to the line.
Since one of the points does not belong to the line, then the equation is not a good model.
Answer:
It is not a good model. One of the points does not belong to the line.
Answer: DA:FA=KE:EF, DF:DA=KF:KE and FA:DA=EF:KE are correct.
Explanation: Since,
and
are similar triangles.
Because,
and
(because EA and KD are parallels. And,
is common angle for these triangles.
Therefore, according to the property of similar triangles.
FE:EK= FA:AD, FE:FK=FA:FD and DF:DA=KF:KE .
Thus, first, second and third options are correct.