tanα=1/7,α为锐角sinα=1/√50,cosα=7/√50,tanβ=1/3,sinβ=1/√10,cosβ=3/√10sin2β=2sinβcosβ=3/5,cos2β=2cos²β-1=4/5sin(α+2β)=sinαcos2β+cosαsin2β=1/√50*(4/5)+7/√50*(3/5)=25/(5*√50)...