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问题：已知α为锐角,且sin^2α-sinαcosα-2cos^2=0.(1)求tanα的值.(2)求sin[α-(π/3)]
答案：↓↓↓ 万平英的回答： 网友采纳 1.sin^2α-sinαcosα-2cos^2=sin^2a-cos^2a-1/2(sin2a)-cos^2a+1-1 =-cos2a-1/2(sin2a)-1=0 cos2a+1/2(sin2a)=-1 (1-tan^2a)/(1+tan^2a)-0.5[2tana/(1+tan^2a)]=-1 1-tan^2a-tana=-1-tan^2a tana=2 2.已知α为锐角,则sina=2/根号5cosa=1/根号5 sina[a-(TT/3)]=sinacos60-sin60cosa=(1-根号3）/2根号5 | 
