A manuscript is sent to a typing firm consisting of typists A, B, and C. If it is typed by A, then the number of errors made is
a Poisson random variable with mean 2.6: if typed by B, then the number of errors is a Poisson random variable with mean 3: and if typed by C, then it is a Poisson random variable with mean 3.4. Let X denote the number of errors in the typed manuscript. Assume that each typist is equally likely to do the work. Find E[X] and Var[X].
1 answer:
You might be interested in
9514 1404 393
Answer:
77/85
Step-by-step explanation:
<u>Given</u>:
cos(A) = 4/5
sin(B) = 15/17
<u>Find</u>:
cos(A-B)
<u>Solution</u>:
From your knowledge of Pythagorean triples, you know that one of them is (3, 4, 5) and another is (8, 15, 17). Using your imagination, or by drawing the triangles, you can determine the needed trig functions to be ...
sin(A) = 3/5
cos(B) = 8/17
__
Alternatively, you can use the Pythagorean identity to find ...
sin(A) = √(1 -cos²(A)) = √(1 -(4/5)²) = √(9/25) = 3/5
cos(B) = √(1 -sin²(B)) = √(1 -(15/17)²) = √(64/289) = 8/17
__
Then application of the angle difference formula is straightforward.
cos(A -B) = cos(A)cos(B) +sin(A)sin(B)
cos(A -B) = (4/5)(8/17) +(3/5)(15/17) = (32 +45)/85
cos(A -B) = 77/85
_____
Some graphing calculators can express the result ...
cos(arccos(4/5) -arcsin(15/17)) ≈ 0.90588235294
... as the fraction 77/85
