Try this beautiful problem from Geometry based on the area of Region

## Find the area – AMC-8, 2017- Problem 25

In the figure shown,Â US and UT andÂ are line segments each of length 2, and\(\angle TUS=60^{\circ}\). ArcsÂ TR and SR Â and are each one-sixth of a circle with radius 2. What is the area of the figure shown?

- (4 – \(\frac{4\pi}{3})\)
- (\(4\sqrt3\) – \(\frac{4\pi}{3})\)
- (\(4\sqrt3\) – \(4\pi\)

**Key Concepts**

Geometry

Triangle

Circle

## Check the Answer

But try the problem first…

Answer: (\(4\sqrt3\) – \(\frac{4\pi}{3})\)

AMC-8 (2017) Problem 25

Pre College Mathematics

## Try with Hints

First hint

We have to find out the shaded region. The above diagram is not a standard geometrical figure (such as triangle, square or circle, etc.). So we can not find out the area of the shaded region by any standard formula.

Now if we extend US and UT and joined XY( shown in the above figure ) then it becomes a Triangle shape i.e \(\triangle UXY\) and region XSR and region TRY are circular shapes. Now you have to find out the area of these geometrical figures…

Can you now finish the problem ……….

Second Hint

Given that US and UT andÂ are line segments each of length 2 and ArcsÂ TR and SR Â andÂ are each one-sixth of a circle with radius 2. Therefore UX=2+2=4,UY=2+2=4 and SX=2+2=4.Therefore \(\triangle UXY\) is an equilateral triangle with side length 4 and area of equilateral triangle =\(\frac{\sqrt 3}{4} (side)^2\) and the region XSR and region TRY are each one-sixth of a circle with radius 2.nor area of the circle =\(\pi (radius)^2\)

can you finish the problem……..

Final Step

The area of the \(\triangle UXY=\frac{\sqrt 3}{4} (4)^2=4\sqrt3\) sq.unit

Now area of (region SXR + region TRY)=\(2 \times \frac{\pi (2)^2}{6}=\frac{4\pi}{3}\)

Therefore the area of the region USRT=Area of \(\triangle UXY\)- (region SXR + region TRY)=(\(4\sqrt3\) – \(\frac{4\pi}{3})\)

## Other useful links

- https://www.cheenta.com/angles-of-star-amc-8-2000-problem-24/
- https://www.youtube.com/watch?v=LArf0rlglzk

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