Please help me out quickly!

since we know the radius of the larger semicircle is 8, thus its diameter is 16, which is the length of one side of the equilateral triangle. We also know the smaller semicircle has a radius of 1/3, and thus a diameter of 2/3, namely the lenght of one side of the small equilateral triangle.

now, if we just can get the area of the larger figure and the area of the smaller one and subtract the smaller from the larger, we'll be in effect making a hole/gap in the larger and what's leftover is the shaded figure.

$\bf \stackrel{\textit{area of a semi-circle}}{A=\cfrac{1}{2}\pi r^2\qquad r=radius}~\hspace{10em}\stackrel{\textit{area of an equilateral triangle}}{A=\cfrac{s^2\sqrt{3}}{4}\qquad s=\stackrel{side's}{length}} \\\\[-0.35em] ~\dotfill\\\\ \stackrel{\textit{\Large Areas}}{\left[ \stackrel{\textit{larger figure}}{\cfrac{1}{2}\pi 8^2~~+~~\cfrac{16^2\sqrt{3}}{4}} \right]\qquad -\qquad \left[ \cfrac{1}{2}\pi \left( \cfrac{1}{3} \right)^2 +\cfrac{\left( \frac{2}{3} \right)^2\sqrt{3}}{4}\right]}$

$\bf \left[ 32\pi +64\sqrt{3} \right]\qquad -\qquad \left[ \cfrac{\pi }{18}+\cfrac{\frac{4}{9}\sqrt{3}}{4} \right] \\\\\\ \left[ 32\pi +64\sqrt{3} \right]\qquad -\qquad \left[ \cfrac{\pi }{18}+\cfrac{\sqrt{3}}{9} \right]~~\approx~~ 211.38 - 0.37~~\approx~~ 211.01$

3 0

4 years ago

Marris decides to bake his parents a cookie in the shape of a regular dodecagon (12‑gon) for their 12-day anniversary.

allochka39001 [22]

Answer:

The answer to each question is:

A.) 403.2 $cm^{2}$
B.) 100. 8 $cm^{2}$

Step-by-step explanation:

A.) To obtain the area of the dodecagon, you can use the next formula:

Area of a dodecagon = 6 * apothem * edge

In the exercise, we have the edge (6 cm), but, to find the apothem of a dodecagon, that is the distance between the center of the polygon, and the middle point of each side, you can use the next formula:

Apothem = Edge * $\frac{2+\sqrt{3}}{2}$

If we replace the value of the edge, we obtain:

Apothem = 6 cm * $\frac{2+\sqrt{3}}{2}$
Apothem = 11.2 cm (approximately).

With this data, we can find the area:

Area of a dodecagon = 6 * apothem * edge
Area of a dodecagon = 6 * 11.2 cm * 6 cm
Area of a dodecagon = 403.2 $cm^{2}$

Then, the area of the dodecagon is 403.2 $cm^{2}$ approximately.

B.) As the area obtained is for 12 pieces, when the parents ate 9 pieces, just left 3 pieces, with these values you can make a rule of three.

If:

12 pieces = 403.2 $cm^{2}$
3 pieces = X

Then:

X = (3 * 403.2 $cm^{2}$ ) / 12
X = 1209.6 $cm^{2}$ / 12
X = 100. 8 $cm^{2}$

In this form, when the cookie has 3 pieces, its area is 100. 8 $cm^{2}$ approximately.

5 0

3 years ago

Please help me out quickly!​

Please help me out quickly!