设所求直线的倾斜角为β,已知直线的倾斜角为α,依题意知β=2α,且tanα=1/4,又所求直线的斜率k=tanβ=tan2α=2tanα/(1-tan²α)=2*(1/4)/[1-(1/4)²]=(1/2)/[1-(1/16)]=(1/2)/(15/16)=8/15.按点斜式可写出...