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2 years ago

(x - 2) + (y - 9) = 4 center and the radius of the circle

Mathematics

1 answer:

storchak [24]2 years ago

7 0

Answer:

The center is (2, 9) and the radius is 2.

Step-by-step explanation:

The general equation for a circle is (x - h) + (y - k) = r^2

(h, k) is the center and r^2 is the radius squared. So, in this case (h, k) is (2, 9) and r^2 is 4 so r = 2.

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A sailboat started his journey at 6:30 am and reached his destination at 11:45 pm.If the distance of the journey was 1276.5, wha

attashe74 [19]

Answer:

74 mph

Step-by-step explanation:

step 1

Find the total time

A sailboat started his journey at 6:30 am and reached his destination at 11:45 pm

from 6:30 am to 12:00 pm ----> there are 5 hours + 30 minutes=5.5 hours

from 12:00 pm to 11:45 pm ----> there are 11 hours + 45 minutes=11.75 hours

The total time is

5.5+11.75=17.25 hours

step 2

Find the average speed

we know that

The average speed is equal to divide the total distance by the total time

$speed=\frac{1,276.5}{17.25}= 74\ mph$

4 0

2 years ago

Lin runs 5 laps around a track in 8 minutes.

andrezito [222]

Answer:

To run one lap Lin takes 1.6 minutes.

Step-by-step explanation:

To find this answer you would do 8 divided by 5. Always remember when dividing time goes first unless the instructions / directions / your teacher says differently. So, when you do 8 divided by 5 the answer you get is 1.6, and there is your answer. Also to check your answer you can do 1.6 times 5, and you get 8, so you know that 1.6 is the correct answer.

5 0

2 years ago

Let z=3+i, then find a. Z² b. |Z| c.<img src="https://tex.z-dn.net/?f=%5Csqrt%7BZ%7D" id="TexFormula1" title="\sq

zysi [14]

Given z = 3 + i, right away we can find

(a) square

z ² = (3 + i )² = 3² + 6i + i ² = 9 + 6i - 1 = 8 + 6i

(b) modulus

|z| = √(3² + 1²) = √(9 + 1) = √10

(d) polar form

First find the argument:

arg(z) = arctan(1/3)

Then

z = |z| exp(i arg(z))

z = √10 exp(i arctan(1/3))

z = √10 (cos(arctan(1/3)) + i sin(arctan(1/3))

Any complex number has 2 square roots. Using the polar form from part (d), we have

√z = √(√10) exp(i arctan(1/3) / 2)

and

√z = √(√10) exp(i (arctan(1/3) + 2π) / 2)

Then in standard rectangular form, we have

$\sqrt z = \sqrt[4]{10} \left(\cos\left(\dfrac12 \arctan\left(\dfrac13\right)\right) + i \sin\left(\dfrac12 \arctan\left(\dfrac13\right)\right)\right)$

and

$\sqrt z = \sqrt[4]{10} \left(\cos\left(\dfrac12 \arctan\left(\dfrac13\right) + \pi\right) + i \sin\left(\dfrac12 \arctan\left(\dfrac13\right) + \pi\right)\right)$

We can simplify this further. We know that z lies in the first quadrant, so

0 < arg(z) = arctan(1/3) < π/2

which means

0 < 1/2 arctan(1/3) < π/4

Then both cos(1/2 arctan(1/3)) and sin(1/2 arctan(1/3)) are positive. Using the half-angle identity, we then have

$\cos\left(\dfrac12 \arctan\left(\dfrac13\right)\right) = \sqrt{\dfrac{1+\cos\left(\arctan\left(\dfrac13\right)\right)}2}$

$\sin\left(\dfrac12 \arctan\left(\dfrac13\right)\right) = \sqrt{\dfrac{1-\cos\left(\arctan\left(\dfrac13\right)\right)}2}$

and since cos(x + π) = -cos(x) and sin(x + π) = -sin(x),

$\cos\left(\dfrac12 \arctan\left(\dfrac13\right)+\pi\right) = -\sqrt{\dfrac{1+\cos\left(\arctan\left(\dfrac13\right)\right)}2}$

$\sin\left(\dfrac12 \arctan\left(\dfrac13\right)+\pi\right) = -\sqrt{\dfrac{1-\cos\left(\arctan\left(\dfrac13\right)\right)}2}$

Now, arctan(1/3) is an angle y such that tan(y) = 1/3. In a right triangle satisfying this relation, we would see that cos(y) = 3/√10 and sin(y) = 1/√10. Then

$\cos\left(\dfrac12 \arctan\left(\dfrac13\right)\right) = \sqrt{\dfrac{1+\dfrac3{\sqrt{10}}}2} = \sqrt{\dfrac{10+3\sqrt{10}}{20}}$