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erastova [34]
3 years ago
7

Question is 15 points

Mathematics
1 answer:
mihalych1998 [28]3 years ago
4 0

This is a doozy so pay attention. First thing you have to recognize is that is a trig identity, the sum identity for cosine to be exact. That formula is

cos(\alpha +\beta )=cos\alpha cos\beta -sin\alpha sin\beta.

So that means you need to find the cosine of alpha and the sin of beta. We are given the sin of alpha being 4/5 in the first quadrant. If you set up the sin ratio which is side opposite over hypotenuse of a right triangle, you put the 4 on the side opposite the reference angle, alpha, and the hypotenuse of 5 on the terminal ray and then you have to find the missing side of the right triangle you created. Using Pythagorean's theorem, you find that the missing side, which is the adjacent side to alpha, is 3. Now you can find the cosine of alpha as well, since cosine is the side adjacent, 3, over the hypotenuse, 5. So far wwe have

sin\alpha =\frac{4}{5} and

cos\alpha =\frac{3}{5} for that first angle. Now moving on to the second angle. The cosine of beta is side adjacent, 5, over the hypotenuse, 13, and we are missing the side opposite the reference angle beta. Using Pythagorean's theorem again to find the side opposite, we have that that side measures 12. Now we can find the sine of beta using that opposite side, 12, over the hypotenuse, 13. What we have now is

cos\beta =\frac{5}{13} and

sin\beta =\frac{12}{13}. According to the identity, we have to multiply those ratios now:

(\frac{3}{5}*\frac{5}{13})-(\frac{4}{5}*\frac{12}{13}).

When you do that you get

\frac{3}{13}-\frac{48}{65}.

Of course in order to subtract those 2 fractions you need a common denominator which is 65 so

\frac{15}{65}-\frac{48}{65} which gives you a final answer of -\frac{33}{65} which is the first choice given above. There you go!

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f the dean wanted to estimate the proportion of all students receiving financial aid to within 3% with 99% reliability, how many
Oksanka [162]

Answer:

n=1849

Step-by-step explanation:

Previous concepts

A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".  

The margin of error is the range of values below and above the sample statistic in a confidence interval.  

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".  

The population proportion have the following distribution

p \sim N(p,\sqrt{\frac{p(1-p)}{n}})

Solution to the problem

In order to find the critical value we need to take in count that we are finding the interval for a proportion, so on this case we need to use the z distribution. Since our interval is at 99% of confidence, our significance level would be given by \alpha=1-0.99=0.01 and \alpha/2 =0.005. And the critical value would be given by:

z_{\alpha/2}=-2.58, z_{1-\alpha/2}=2.58

The margin of error for the proportion interval is given by this formula:  

ME=z_{\alpha/2}\sqrt{\frac{\hat p (1-\hat p)}{n}}    (a)  

And on this case we have that ME =\pm 0.03 and we are interested in order to find the value of n, if we solve n from equation (a) we got:  

n=\frac{\hat p (1-\hat p)}{(\frac{ME}{z})^2}   (b)  

Assuming that the proportion is estimated \hat p =0.5. And replacing into equation (b) the values from part a we got:

n=\frac{0.5(1-0.5)}{(\frac{0.03}{2.58})^2}=1849  

And rounded up we have that n=1849

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3 years ago
Simplify 6 - (-2) - 3(-5).<br> -11<br> -7<br> 19<br> 23
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6 - (-2) - 3(-5) = (6 + 2) + 15 = 8 + 15 = 23

Your answer is D. the last one :)
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