First one:
cos(A)=AC/AB=3/4.24
cos(B)=BC/AB=3/4.24
Cos(A)/cos(B)=AC/AB / (BC/AB) = AC/AB * AB/BC = AC/BC=3/3=1
Second one:
To solve this problem, we have to ASSUME AFE is a straight line, i.e. angle EFB is 90 degrees. (this is not explicitly given).
If that's the case, AE is a transversal of parallel lines AB and DE.
And Angle A is congruent to angle E (alternate interior angles).
Therefore sin(A)=sin(E)=0.5
Answer:
see below
Step-by-step explanation:

we need to simplify that

so we can continue

and we can put all together

Answer:
The probability that the instrument does not fail in an 8-hour shift is 
The probability of at least 1 failure in a 24-hour day is 
Step-by-step explanation:
The probability distribution of a Poisson random variable X representing the number of successes occurring in a given time interval or a specified region of space is given by the formula:

Let X be the number of failures of a testing instrument.
We know that the mean
failures per hour.
(a) To find the probability that the instrument does not fail in an 8-hour shift, you need to:
For an 8-hour shift, the mean is 

(b) To find the probability of at least 1 failure in a 24-hour day, you need to:
For a 24-hour day, the mean is 

Answer: DL, PS, SL
Step-by-step explanation:
All sides of a square are congruent.