1996 AMC 8 第 17 题

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17.

图形 OPQROPQR 是正方形。点 OO 是原点,点 QQ 的坐标是 (2,2)(2, 2)。点 TT 的坐标应是多少,才能使三角形 PQTPQT 的面积等于正方形 OPQROPQR 的面积?

Figure OPQROPQR is a square. Point OO is the origin, and point QQ has coordinates (2,2)(2, 2). What are the coordinates for TT so that the area of triangle PQTPQT equals the area of square OPQR?OPQR?

(6,0)(-6, 0)

(4,0)(-4, 0)

(2,0)(-2, 0)

(2,0)(2, 0)

(4,0)(4, 0)

答案:C
知识点:坐标几何三角形面积
难度评级:1090
解答:

因为 OPQROPQR 是正方形,且 O=(0,0)O = (0, 0)Q=(2,2)Q = (2, 2),所以 P=(2,0)P = (2, 0)R=(0,2)R = (0, 2),正方形面积为 22=42^2 = 4

三角形 PQTPQT 的竖直底边 PQPQ 长为 22。若 T=(t,0)T = (t, 0) 位于 xx 轴上,它的面积是 122(2t)=2t\tfrac12 \cdot 2 \cdot (2 - t) = 2 - t。令 2t=42 - t = 4,得到 t=2t = -2,所以 T=(2,0)T = (-2, 0)

所以正确答案是 C

Since OPQROPQR is a square with O=(0,0)O = (0, 0) and Q=(2,2)Q = (2, 2), we have P=(2,0)P = (2, 0) and R=(0,2)R = (0, 2), so the area is 22=42^2 = 4.

Triangle PQTPQT has vertical base PQPQ of length 22, and T=(t,0)T = (t, 0) lies on the xx-axis. Its area is 122(2t)=2t\tfrac12 \cdot 2 \cdot (2 - t) = 2 - t. Setting 2t=42 - t = 4 gives t=2t = -2, so T=(2,0)T = (-2, 0).

Thus, the correct answer is C .

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