If the direction ratios of two perpendicular straight lines are given by 1,θ,θ3−θ+7 and 0,4,θ  where  θ≠0, thenTan−1θ−θ311=

The lines having direction ratios a1,b1,c1and a2,b2,c2are perpendicular then a1a2+b1b2+c1c2=0Hence,4θ+θ4−θ2+7θ=0θ3−θ+11=0θ−θ311=1Therefore, Tan−1θ−θ311=π4