All categories

3 years ago

If cos x cos (pi/7)+sin x sin(pi/7)=-(sqrt 2)/2,then x can equal

1 answer:

3 0

Main formula cos (a - b) =cosacosb + sina sinb
arccos(-x) = pi -arccosx

cos x cos (pi/7)+sin x sin(pi/7) = cos(x-pi/7)

so cos(x-pi/7) = -(sqrt 2)/2, x -pi/7 = arc cos[-(sqrt 2)/2 ]= pi - arc cos[(sqrt 2)/2 ]

arc cos[(sqrt 2)/2 ] = Pi/4 + 2kpi, and then x -pi/7 = pi - pi/4 +2kpi,
implies x= -pi/7 + pi - pi/4 = -pi/7 + 3pi/4 = -19pi/28 + 2kpi

You might be interested in

......................................

Naddika [18.5K]

Answer:

D. f(x) = x - 4

Step-by-step explanation:

If you plug in the x values for the expression x - 4:

3 - 4 = -1
4 - 4 = 0
5 - 4 = 1
6 - 4 = 2
This means that the function rule is f(x) = x - 4
Hope this helps :)

8 0

1 year ago

Read 2 more answers

A researcher wishes to estimate the proportion of X-ray machines that malfunction. A random 275 sample of machines is taken, and

Dominik [7]

Answer:

Following are the solution to the given question:

Step-by-step explanation:

$95\%$ Confidence Interval for both the percentage of all x-ray machines

p = the machinery's share is not working:

$= \frac{228}{275}\\\\ = 0.829$

$\text{Margin of Error} = Z_{(\frac{\alpha}{2})} \times \sqrt{( p \times (1-p)}{n})$

$= 1.96 \times \sqrt{(0.829 \times \frac{0.171}{275})} \\\\= 1.96 \times 0.023 \\\\= 0.045$

Lower $95\%$ Confidence interval = p - error margin $= 0.829 - 0.045 = 0.784$

Upper $95\%$ Confidence Interval = p + error margin $= 0.829 + 0.045 = 0.874$

So, $95\%$ Confidence Interval $= ( 0.78 , 0.87 )$

4 0

2 years ago

Help me with math please

DENIUS [597]

(-3^3+2 · -2^2)^2-4^4

(-27+2 · -4)^2-4^4

(-27+(-8))^2-4^4

-35^2-4^4

1225-256

969

8 0

2 years ago

What is the approximate surface area of a sphere with a circumference of 37.68

sergij07 [2.7K]

We must find the radius so we can plug this into the formula for surface area.

Circumference = $2 \pi r$
$37.68 = 2 \pi r \\ r = 37.68/2 \pi$

We are going to plug this in as our radius for the most accurate answer.

The surface area of a sphere is $4 \pi r^{2}$

Surface Area = $4 \pi ( \frac{37.68}{2 \pi }) ^{2}$ ≈ 451.93 units

6 0

3 years ago

The vertex of the parabola below is at the point (4, -1). Which of the equations below could be the one for this parabola?

AlekseyPX

Answer:

The answer is B

Step-by-step explanation:

6 0

2 years ago