解çï¼
设A(x1ï¼y1) Gè¿Dç¹ä½DEåç´äºOC交xè½´äºEç¹
对y=sinxè¿è¡æ±å¯¼ï¼å³yâ=cosx
å³ABçæç=cosx1=OPçæç=2/Ï
æ以y1=sinx1= â(1-cosx1*cosx1)=â(1-4/Ï^2 )
BA*BC=BA*cosθ*BC=BC^2
BC/OE=AC/OE=y1/(Ï/2)
æ以BC^2=Ï^2/4-1
第äºé¢ï¼
f(x)=æ ¹3sinwx+coswx=2sin(wx+Ï/6)
.y=f(x)çå¾åä¸ç´çº¿y=2ç两个ç¸é»äº¤ç¹çè·ç¦»çäº,
æ以,w=2Ï/Ï=2
f(x)=2sin(2x+Ï/6)
-Ï/2+2kÏ<=2x+Ï/6<=Ï/2+2kÏ
-Ï/3+kÏ<=x<=Ï/6+kÏ
1.å®ä¹å为xä¸çäº0
f(-x)=x2-a/x
å½a=0æ¶ï¼f(-x)=x2=f(x),æ¤æ¶f(x)为å¶å½æ°
å½a>0æa<0æ¶,f(x)为éå¥éå¶å½æ°
2.æ±å¯¼ï¼
f(x)ç导æ°=2x-a/x2>0,
a<2ï¼xçä¸æ¬¡æ¹ï¼
åå 为x为[2ï¼+â)
æ以a<16
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