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3 years ago

What is the half-angle of tangent 22.5 (degrees)?

Mathematics

2 answers:

Sergio039 [100]3 years ago

6 0

Find tan (22.5)

Answer: #-1 + sqrt2#

Explanation:

Call tan (22.5) = tan t --> tan 2t = tan 45 = 1

Use trig identity: # tan 2t = (2tan t)/(1 - tan^2 t)# (1)

#tan 2t = 1 = (2tan t)/(1 - tan^2 t)# -->
--> #tan^2 t + 2(tan t) - 1 = 0#
Solve this quadratic equation for tan t.

#D = d^2 = b^2 - 4ac = 4 + 4 = 8# --> #d = +- 2sqrt2#
There are 2 real roots:
tan t = -b/2a +- d/2a = -2/1 + 2sqrt2/2 = - 1 +- sqrt2
Answer:
#tan t = tan (22.5) = - 1 +- sqrt2#
Since tan 22.5 is positive, then take the positive answer:
tan (22.5) = - 1 + sqrt2

irina [24]3 years ago

6 0

Since 22.522.5 is not an angle where the values of the six trigonometric functions are known, try using half-angle identities.22.522.5 is not an exact angleFirst, rewrite the angle as the product of 1212 and an angle where the values of the six trigonometric functions are known. In this case, 22.522.5 can be rewritten as (12)⋅4512⋅45.tan((12)⋅45)tan12⋅45Use the half-angle identity for tangent to simplify the expression. The formula states that tan(θ2)=sin(θ)1+cos(θ)tanθ2=sinθ1+cosθ.sin(45)1+cos(45)sin451+cos45Simplify the result.
√2−1

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Kate had 70 brooms; Alisa had 20 more brooms than Kate. What was the ratio of Kate’s brooms to Alisa’s brooms?

Shalnov [3]

Answer:

7:9

Step-by-step explanation:

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3 years ago

An automobile club reported that the average price of regular gasoline in a certain state was $2.61 per gallon. The following d

laila [671]

Answer:

$2.618-2.98\frac{0.078}{\sqrt{15}}=2.56$

$2.618+2.98\frac{0.078}{\sqrt{15}}=2.68$

So on this case the 99% confidence interval would be given by (2.56;2.68)

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".

$\bar X$ represent the sample mean for the sample

$\mu$ population mean (variable of interest)

s represent the sample standard deviation

n represent the sample size

Solution to the problem

The confidence interval for the mean is given by the following formula:

$\bar X \pm t_{\alpha/2}\frac{s}{\sqrt{n}}$ (1)

In order to calculate the mean and the sample deviation we can use the following formulas:

$\bar X= \sum_{i=1}^n \frac{x_i}{n}$ (2)

$s=\sqrt{\frac{\sum_{i=1}^n (x_i-\bar X)}{n-1}}$ (3)

The mean calculated for this case is $\bar X=2.618$

The sample deviation calculated $s=0.078$

In order to calculate the critical value $t_{\alpha/2}$ we need to find first the degrees of freedom, given by:

$df=n-1=15-1=14$

Since the Confidence is 0.99 or 99%, the value of $\alpha=0.01$ and $\alpha/2 =0.005$ , and we can use excel, a calculator or a table to find the critical value. The excel command would be: "=-T.INV(0.005,14)".And we see that $t_{\alpha/2}=2.98$