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Sergeeva-Olga [200]
3 years ago
14

The exact vaule of cos(247.5 degrees)

Mathematics
1 answer:
Leni [432]3 years ago
8 0
cos(247.5 deg)=cos( \frac{495deg}{2})
                         =  - \sqrt{ \frac{1+cos(495deg)}{2} }  
                         = -\sqrt{ \frac{1- \frac{ \sqrt{2} }{2} }{2} } 
                         =  \frac{ \sqrt{2- \sqrt{2} } }{2}
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The measures of 6 of the interior angles of a heptagon are: 120°, 150°, 135°, 170°, 90°, and 125°. What is the measure of the la
Lilit [14]
1. consider one angle of a (convex) heptagon. From that angle you can construct 7-3=4 diagonals. (-3 because we cannot create diagonals with the adjacent vertices and the angle itself )

2. 4 diagonals create 5 triangular regions. (check the picture)

3. So the sum of the measures of the interior angles of the heptagon is 180°*5=900°.

4. The measure of the remaining 7th interior angle is 900°-(120+150+135+170+90+125)°=110°.

5. The largest exterior angle is when the interior angle is the smallest.

6. The smallest interior angle is 90°, so the largest exterior angle is 180°-90°=90°


Answer: 90°

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2 years ago
A phone manufacturer wants to compete in the touch screen phone market. He understands that the lead product has a battery life
alisha [4.7K]

Answer:

a)

The null hypothesis is H_0: \mu \leq 10

The alternative hypothesis is H_1: \mu > 10

b-1) The value of the test statistic is t = 1.86.

b-2) The p-value is of 0.0348.

Step-by-step explanation:

Question a:

Test if the battery life is more than twice of 5 hours:

Twice of 5 hours = 5*2 = 10 hours.

At the null hypothesis, we test if the battery life is of 10 hours or less, than is:

H_0: \mu \leq 10

At the alternative hypothesis, we test if the battery life is of more than 10 hours, that is:

H_1: \mu > 10

b-1. Calculate the value of the test statistic.

The test statistic is:

We have the standard deviation for the sample, so the t-distribution is used to solve this question

t = \frac{X - \mu}{\frac{s}{\sqrt{n}}}

In which X is the sample mean, \mu is the value tested at the null hypothesis, s is the standard deviation and n is the size of the sample.

10 is tested at the null hypothesis:

This means that \mu = 10

In order to test the claim, a researcher samples 45 units of the new phone and finds that the sample battery life averages 10.5 hours with a sample standard deviation of 1.8 hours.

This means that n = 45, X = 10.5, s = 1.8

Then

t = \frac{X - \mu}{\frac{s}{\sqrt{n}}}

t = \frac{10.5 - 10}{\frac{1.8}{\sqrt{45}}}

t = 1.86

The value of the test statistic is t = 1.86.

b-2. Find the p-value.

Testing if the mean is more than a value, so a right-tailed test.

Sample of 45, so 45 - 1 = 44 degrees of freedom.

Test statistic t = 1.86.

Using a t-distribution calculator, the p-value is of 0.0348.

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2 years ago
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