Thin Plates with Constant Density (Calculus II)

dm41nes
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Thank you in advance for the help!

Homework Statement



Find the center of mass of a thin plate of constant density (delta) covering the given region.
The region bounded by the parabola y= x - x2 and the line y= -x



Homework Equations



See attachment question 15 p1

The Attempt at a Solution



See attachment question 15 p2
 

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I like your last solution on attachment 2 except...
Integral from 0 to 2 (x-x^2-x) dx is not Int (2x - x^2) dx
I think you just have an algebra mistake there.
 
Thank you, well it was x-x^2-(-x). So, I added the double negative to the other x. Thats how I was able to get 2x.


Are these forumulas a certified way to find the center of mass?
 
Prove $$\int\limits_0^{\sqrt2/4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx = \frac{\pi^2}{8}.$$ Let $$I = \int\limits_0^{\sqrt 2 / 4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx. \tag{1}$$ The representation integral of ##\arcsin## is $$\arcsin u = \int\limits_{0}^{1} \frac{\mathrm dt}{\sqrt{1-t^2}}, \qquad 0 \leqslant u \leqslant 1.$$ Plugging identity above into ##(1)## with ##u...
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