If 1,−1,1 and 2,−3,5 are direction ratios of two lines, then the angle between them is

If θ is the acute angle between two lines having direction ratios a1,b1,c1and a2,b2,c2 then cosθ=a1a2+b1b2+c1c2a12+b12+c12⋅a22+b22+c22Hence,cosθ=2+3+51+1+1⋅4+9+25=103⋅38=5257Therefore,θ=cos−15257