1．A semicircle is inscribed in an isosceles triangle with base 16 and height 15 so that the diameter of the semicircle is contained in the base of the triangle as shown.What is the radius of the semicircle？（　　）
一個(gè)半圓內(nèi)接于一個(gè)底邊為16，高為15的等腰三角形中，使得半圓的直徑包含在三角形的底邊上，如圖所示。這個(gè)半圓的半徑是多少？（　?。?/div>

2．In the figure shown,US and UT are line segments each of length 2，and m∠TUS=60°.Arcs TR and SR are each one-sixth of a circle with radius 2.What is the area of the region shown？（　?。?br />如圖所示，US和UT是長(zhǎng)度都為2的線段，且∠TUS=60°。圓弧TR和SR的都是半徑為2的圓的六分之一。這所示區(qū)域的面積是多少？（　?。?/div>

3．A straight one-mile stretch of highway,40 feet wide,is closed.Robert rides his bike on a path composed of semicircles as shown.If he rides at 5 miles per hour,how many hours will it take to cover the one-mile stretch？（　?。?br />Note：1 mile=5280 feet
一段直線的公路，長(zhǎng)一英里、寬40英尺，被封閉了。Robert騎自行車走的路線是由如圖所示的半圓組成的。如果他以5英里每小時(shí)的速度騎行，他需要多少小時(shí)才能走完這一英里的路段？（　?。?br />注：1英里=5280英尺。
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