cos三分之π

樊类晏3636COSπ/3 等于?怎么算得? -
鞠战畅17320855482 ______ π=180°,COSπ/3=COS60°=1/2

樊类晏3636cosα= - 17分之8,且α是第二象限角,那么cos(3分之π - α)= cosα= - 17分之8,且α是第二象限角,那么cos(3分之π - α)= -
鞠战畅17320855482 ______[答案] sinα=√[1-(cosα)^2]=15/17,(第二象限角正弦为正) cos(π/3-α)=cosαcos(π/3)+sinαsin(π/3) =-8/17*(1/2)+(15/17)*√3/2 =(15√3-8)/34.

樊类晏3636已知函数F(X)=cos(三分之π+x)cos(三分之π - x)=根三sinxcosx+四分之一 -
鞠战畅17320855482 ______ 因为cos(a+b)=cosacosb-sinasinb cos(a-b)=cosacosb+sinasinb 相加得cos(a+b)+cos(a-b)=2cosacosb 即cosacosb=[cos(a+b)+cos(a-b)]/2 所以f(x)=cos(π/3+x)cos(π/3-x)=[cos(π/3+x+π/3-x)+cos(π/3+x-π/3+x)]/2=[cos(2π/3)+cos2x]/2=(cos2x-1/2)/2=cos2x/2-1/4 如果不懂,请追问,祝学习愉快!

樊类晏3636cos3分之5π等于多少? -
鞠战畅17320855482 ______[答案] cos(5π/3)=cos(2π-π/3)=cos(-π/3)=cos(π/3)=1/2

樊类晏3636cos3分之50兀等于多少 -
鞠战畅17320855482 ______ cos(50π/3)=cos(16π+2π/3)=cos(2π/3)=-1/2

樊类晏3636cos(3分之5π)是等于2分之一吗? -
鞠战畅17320855482 ______[答案] cos(3分之5π)=cosπcos2π/3-sinπsin2π/3=-cos2π/3=cosπ/3=1/2

樊类晏3636cos三分之十π得多少? -
鞠战畅17320855482 ______[答案] cos(10π/3)=cos(4π-2π/3)=cos(2π/3)=-1/2

樊类晏3636cos3分之2π等于几 -
鞠战畅17320855482 ______[答案] cos(2π/3)=-cos(π-2π/3)=-cos(π/3)=-1/2

樊类晏3636cos8π/3= -
鞠战畅17320855482 ______[答案] 原式=cos(2π+2π/3) =cos(2π/3) =-1/2

樊类晏3636cos三分之十π得多少? -
鞠战畅17320855482 ______ cos三分之十π=cos三分之四π=-cos三分之一π=-1/2