**PLEASE HELP**
1 answer:
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You know that 
so 
.
Area of a shaded region is:
![$A=\int\limits_0^k\dfrac{y^2}{4}\,dy=\frac{1}{4}\int\limits_0^ky^2\,dy=\frac{1}{4}\left[\frac{y^3}{3}\right]_0^k=\frac{1}{4}\left[\frac{k^3}{3}-\frac{0^3}{3}\right]=\frac{1}{4}\cdot\dfrac{k^3}{3}=\boxed{\frac{k^3}{12}}](https://tex.z-dn.net/?f=%24A%3D%5Cint%5Climits_0%5Ek%5Cdfrac%7By%5E2%7D%7B4%7D%5C%2Cdy%3D%5Cfrac%7B1%7D%7B4%7D%5Cint%5Climits_0%5Eky%5E2%5C%2Cdy%3D%5Cfrac%7B1%7D%7B4%7D%5Cleft%5B%5Cfrac%7By%5E3%7D%7B3%7D%5Cright%5D_0%5Ek%3D%5Cfrac%7B1%7D%7B4%7D%5Cleft%5B%5Cfrac%7Bk%5E3%7D%7B3%7D-%5Cfrac%7B0%5E3%7D%7B3%7D%5Cright%5D%3D%5Cfrac%7B1%7D%7B4%7D%5Ccdot%5Cdfrac%7Bk%5E3%7D%7B3%7D%3D%5Cboxed%7B%5Cfrac%7Bk%5E3%7D%7B12%7D%7D%20)
so k:
![\dfrac{k^3}{12}=\dfrac{9}{4}\\\\\\k^3=\dfrac{9\cdot12}{4}\\\\\\k^3=9\cdot3\\\\k^3=3^3\quad|\sqrt[3]{(\ldots)}\\\\\boxed{k=3}](https://tex.z-dn.net/?f=%5Cdfrac%7Bk%5E3%7D%7B12%7D%3D%5Cdfrac%7B9%7D%7B4%7D%5C%5C%5C%5C%5C%5Ck%5E3%3D%5Cdfrac%7B9%5Ccdot12%7D%7B4%7D%5C%5C%5C%5C%5C%5Ck%5E3%3D9%5Ccdot3%5C%5C%5C%5Ck%5E3%3D3%5E3%5Cquad%7C%5Csqrt%5B3%5D%7B%28%5Cldots%29%7D%5C%5C%5C%5C%5Cboxed%7Bk%3D3%7D)
Area of a shaded region is:
so k:
The perimeter of the shaded part is 3.93 cm.
Step-by-step explanation:
Step 1; The perimeter of a circle is calculated by multiply 2π with the radius. This given circle is not an entire circle. An entire circle has an angle if 360° while this has an angle of 50°. So we divide 360° with 50°.
Number of these shapes to form a full circle = 360° / 50° = 7.2. So 7.2 of these shapes will need to be combined to form a full circle. So we can calculate the perimeters of full circles and then divide it by 7.2 to get the parameters of the given sections.
Step 2; The parameter and circumference of a circle are equal. So
The perimeter of shaded region = Perimeter of the entire region - Perimeter of the unshaded region.
The Perimeter of circle with radius 8cm = 2π × 8 = 50.2654 cm.
The perimeter of the given shape = = 6.9813 cm
The perimeter of circle with radius, 3.5cm (8cm - 4.5cm) = 2π × 3.5 = 21.9911 cm,
The perimeter of unshaded region = = 3.0543 cm.
So the perimeter of shaded region = 6.9813 cm - 3.0543 cm = 3.927 cm.
Rounding 3.927 to 3 significant figures we get the perimeter of shaded region equal to 3.93 cm.