问题
选择题
以长为10的线段AB为直径作半圆，则它的内接矩形的面积的最大值为( )
A．10
B．15
C．25
D．50
答案
答案：C
解：如图，
设∠NOB=θ，则矩形面积S=5sinθ•2•5cosθ=50sinθ•cosθ=25sin2θ，
∴sin2θ=1时，函数取得最大值25
故Smax=25
故选C．
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以长为10的线段AB为直径作半圆，则它的内接矩形的面积的最大值为( )
A．10
B．15
C．25
D．50
答案：C
解：如图，
设∠NOB=θ，则矩形面积S=5sinθ•2•5cosθ=50sinθ•cosθ=25sin2θ，
∴sin2θ=1时，函数取得最大值25
故Smax=25
故选C．
Passage 1
Which of the following statement is true a. Dr. Sellers invented the word face blindness. b. Brain scans show that a certain part of the brain of person with face blindness is inactive at all compared with that of a normal person. c. A certain part of the brain of a normal person will react differently to the faces of two different persons. d. Face blindness is accompanied by some symptoms like color blindness.