设A,B为两个有限集,讨论cardA,cardB,CARD[A交B】CARD【A并B】四个数值之间的关系.急

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• 设A,B为两个有限集,讨论cardA,cardB,CARD[A交B】CARD【A并B】四个数值之间的关系.急
• 设A,B为两个有限集,讨论cardA,cardB,CARD[A交B】
• 设X1、X2是方程X^2-Xsin(π/5)+cos(4π/5)=0的两根,求arctanx1+arctanx2的值 设arctanx1=a,arctanx2=b设X1、X2是方程X^2-Xsin(π/5)+cos(4π/5)=0的两根,求arctanx1+arctanx2的值 设arctanx1=a,arctanx2=b,则tana=x1,tanb=x2又因为x1+x2=sin(π/5),x1*x2=cos(4π/5)所以tan(a+b)=(tana+tanb)/(1-tanatanb)=(x1+x2)/(1-x1x2)=sin(π/5)/[1-cos(4π/5)]=tan(π/10)又因为x1+x2=sin(π/5)>0,x1*x2=cos(4π/5)0,x1*x2=cos(4π/5)
• 设x1,x2是方程x²-xsinπ/5+cos4π/5=0的两根,求arctanx1+arctanx2的值RT