tanβ=√2/4α、β都是锐角,则sinβ=1/3,cosβ=2√2/3；即有：sinβ=sinα(2√2/3*cosα-1/3*sinα）=2√2/3*cosαsinα-1/3(1-cos^2α)=1/3 ①；而sin^2(α)+cos^2(α)=1 ...