Q31. In the figure, each side of square A B C D has length 1, the length of line Segment CE is 1, and the length of line segment BE is equal to the length Of line segment DE. What is the area of the triangular region BCE?
图贴不上来,square ABCD,E在c的上方。
a. 1/3 b. (2^-2 )/4 c. 1/2
d. (2^-2)/2 e. 3/4
这个算面积的题目我不会,可能没有理解好题意,答案d,哪位还记得怎么算的?
Area of BCE
= (Area of BDE - Area of BCD) / 2
= [(BD * E to midpoint of BD / 2) - (1 * 1 / 2)] / 2
= {[2^0.5 * (1 + 0.5 * 2^0.5) / 2] - 0.5} / 2
= 2^0.5 / 4
B ?
是不是答案写错了?
设BD中点为M
SBCE=SBEM-SBCM=(2^/2*(1+2^/2))/2-1/4=(2^/2+1/2)/2-1/4=2^/4=(2^/2)/2 d
为什么是减号??
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