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nataly862011 [7]
2 years ago
13

Find the centroid of a semi circle using polar coordinates and a double integral. Given a radius of r, and theta being between 0

and pi.
Mathematics
1 answer:
Fittoniya [83]2 years ago
4 0
The area for a semi circle in Cartesian coordinate system with the flat edge against the x-axis is:A=∫0r2−x2√∫−rrdxdy
Bounding limits for x are from -r to r. And for y, this comes from the equation for a circle:x2+y2=r2
Solve for y:y=±r2−x2−−−−−−√
But since we are only dealing with a semi circle, we can always look at the positive answer. 
To convert to a polar coordinate system, we used some equations you have probably seen:x=rcosθy=rsinθdxdy=rdrdθ
The substitute to convert to polar coordinate system:A=∫0π∫0rrdrdθSolve this for the area.A=πr2/2

To find the x coordinate of the centroid:x=1/A∫∫xdxdyorx=1/A∫0π∫0rrcosθ(rdrdθ)Solve and you will find x = 0 which intuitively makes sense.
Similar for the y coordinate of the centroid:y=1/A∫∫ydxdyory=1/A∫0π∫0rrsinθ(rdrdθ)Solve and you will find y=4r/3π
This means the centroid of a semicircle is at: (0,4r/3π)
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Do not give me any links or files.
Paha777 [63]

Answer:

972 u³

Step-by-step explanation:

The radius is 9 . We can use formula ,

⇒ V = 4/3 π r³

⇒ V = 4/3 × π × 9³

⇒ V = 4 × π × 81 × 3

⇒ V = 972 unit³

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LenKa [72]

Answer:

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A safe has a 4-digit lock code that does not include zero as a digit and no digit is repeated. What is the probability of a lock
Margarita [4]

Answer:

A. 9

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2 years ago
Read 2 more answers
Find w and y, will give brainliest for the correct answer
Alex Ar [27]

Answer: w=12, y=6√3

Step-by-step explanation:

Looking at the figure, we can split the triangle into 2 separate triangles. One on the left and one on the left. The triangle on the right is a 30-60-90 triangle. For this triangle, the hypotenuse is 2x in length. This is directly opposite of the right angle. The leg opposite to 30° is x in length. The leg opposite 60° is x√3 in length. Once you know the length of one side, you can plug in x to find the length of the other legs.

In this case, w and y are located on the same 30-60-90 triangle. Normally we would focus on that triangle to find our values, but in this instance, we don't have any values. We have to use the left triangle to find the leg that both triangles share.

The left triangle is a 45-45-90 triangle. For this triangle, the legs opposite of 45° is x in length. The hypotenuse is x√2. Since we know the hypotenuse, we can use it to find x.

x√2=8

x=8/√2

x=5.7 or 6       [Let's use 6 so that it is easier to work with a whole number]

Now that we know x, we can find w and y. Going back to the right triangle, we know the hypotenuse is 2x. We plug in 6 to find the length.

w=2x

w=2(6)

w=12

We know the leg opposite of 60° is x√3. We can plug in x.

y=6√3

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3 years ago
The population of a town is 15,000. If the population is growing by 5% per year, how long will it take for the population to rea
nikdorinn [45]

by 10 years it'll be 24439 but by 11 it'll be 25661 so it's technically 11 years

6 0
2 years ago
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