An observer from the top of a lighthouse 370 feet above sea level sees two sailboats in the water. The angles of depression to t
he boats are 12 degrees and 10 degrees. How far apart are the boats, to the nearest foot?
1 answer:
Answer:the sailboats are 358 feet apart.
Step-by-step explanation:
The diagram of the triangle representing the situation is shown in the attached photo.
B represents the position of the lighthouse.
D represents the position of the first sailboat.
C represents the position of the second sailboat.
x represents the distance between the two sailboats
We would apply trigonometric ratio
Tan # = opposite/adjacent
For triangle ABD,
Tan 12 = 370/AD
AD = 370/Tan 12 = 370/0.2126 = 1740.357 feet
For triangle ABC,
Tan 10 = 370/AC
AD = 370/Tan 10 = 370/0.1763 = 2098.695 feet
x = AC - AD = 2098.695 - 1740.357 = 358 feet
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Answer:
(a) The variance decreases.
(b) The variance increases.
Step-by-step explanation:
According to the Central Limit Theorem if we have a population with mean <em>μ</em> and standard deviation <em>σ</em> and we take appropriately huge random samples (<em>n</em> ≥ 30) from the population with replacement, then the distribution of the sample mean will be approximately normally distributed.
Then, the mean of the sample mean is given by,
And the standard deviation of the sample mean is given by,
The standard deviation of sample mean is inversely proportional to the sample size, <em>n</em>.
So, if <em>n</em> increases then the standard deviation will decrease and vice-versa.
(a)
The sample size is increased from 64 to 196.
As mentioned above, if the sample size is increased then the standard deviation will decrease.
So, on increasing the value of <em>n</em> from 64 to 196, the standard deviation of the sample mean will decrease.
The standard deviation of the sample mean for <em>n</em> = 64 is:
The standard deviation of the sample mean for <em>n</em> = 196 is:
The standard deviation of the sample mean decreased from 0.7 to 0.4 when <em>n</em> is increased from 64 to 196.
Hence, the variance also decreases.
(b)
If the sample size is decreased then the standard deviation will increase.
So, on decreasing the value of <em>n</em> from 784 to 49, the standard deviation of the sample mean will increase.
The standard deviation of the sample mean for <em>n</em> = 784 is:
The standard deviation of the sample mean for <em>n</em> = 49 is:
The standard deviation of the sample mean increased from 0.2 to 0.8 when <em>n</em> is decreased from 784 to 49.
Hence, the variance also increases.