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nataly862011 [7]
3 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]3 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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Troyanec [42]

Answer:

I dont really understand it but I think it's the first one cuz that's the only one that makes sense to me hope it helped tho:))))))))

8 0
3 years ago
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A restaurant bill before tax is $15.50. How much is a 15% tip for this bill? Be sure to round your answer to the nearest hundred
babymother [125]

Answer: <u><em>17.82</em></u>

Step-by-step explanation:

<em></em>

<em></em>

<em>1.15 x 15.50 = 17.825</em>

<em>17.825 rounded to the nearest hundreth is 17.82</em>

7 0
3 years ago
Help please!!!! Complete the following
sveta [45]
First, "graph" means graph of the given function f(x).  It is not necessary to include the graph with the question because at this level, either the user can "see" the graph mentally, or use technology (calculator or software) to graph the function.

(a) The Leading coefficient test for polynomial functions
The test is as follows.  The sign of the leading coefficient (LC, coefficient of the highest power of the variable) together with the degree (odd or even)  of the polynomial function tells us the end behaviour of the function according to the following table:

LC/degree     Even       Odd
Positive        +inf/+inf    -inf/+inf   
Negative       -inf/-inf     +inf/-inf

It can be easily memorized by comparing with a line or a parabola
y=x (positive leading coefficient, odd degree)  goes from -inf to +inf
y=x^2 (positive leading coefficient, even degree)  goes from +inf to +inf.
Any negative leading coefficient will just invert the signs.

For the given polynomial function
f(x) = x^2(x+2) = x^3+x^2
The leading coefficient is +1 (positive), and degree is three (odd)
So it behaves the same way as a straight line y=x, so the end behviours are
{-inf, +inf}  as x-> {-inf, +inf} respectively.

(b) x-intercepts
Since f(x)=x^2(x+2), the x-intercepts are x=0 (multiplicity 2) and x=-2.
=>
From the left, graph is increasing and crosses x=-2 once from negative to positive, after which graph is decreasing.  At x=0, because of the root with multiplicity 2, graph touches the origin (0,0) and turns back towards +inf.

(c) the y-intercept
from the polynomial f(x)=x^2(x+2)=x^3+x^2 = x^3+x^2+0,
we see that the y-intercept =0 because the "initial value" or the constant term is zero.

5 0
3 years ago
If f(x) = 3x - 2 and g(x) = 2x + 1, find (f+ g)(x).
diamong [38]

(f+g)(x)=3x-2+2x+1=5x-1

3 0
3 years ago
The high school band sold 500 tickets for a concert. The price of an adult ticket was $14.50, and the price of a student ticket
stira [4]

Answer:

14.5a + 9.5s = 5,860

a + s = 500

Step-by-step explanation:

4 0
3 years ago
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