已知ab是锐角,tana=1/7,sinb=(根号10/10),则tan(a+2b)
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已知ab是锐角,tana=1/7,sinb=(根号10/10),则tan(a+2b)
已知ab是锐角,tana=1/7,sinb=(根号10/10),则tan(a+2b)
已知ab是锐角,tana=1/7,sinb=(根号10/10),则tan(a+2b)
sinb=(根号10/10),ab是锐角,则有
cosb=√(1-sin^2b)=3√10/10,
tanb=sinb/cosb=1/3.
tan2b=2tanb/(1-tan^2b)=3/4.
tan(a+2b)=(tana+tan2b)/(1-tana*tan2b)
=(1/7+3/4)/(1-1/7*3/4)
=25/25
=1.
1 用正切的和角公式
tana=1/7, sinb=(根号10/10) cosb=90^(1/2)/10 tanb=1/3 tan2b=2tanb/(1-tan^2b)=1 tan(a+2b)=(tana+tan2b)/(1-tanatan2b)=(1+1/3)/(1-1*1/3)=2