The acute angle between the lines x=-y, z=0 and x=0, z=0 is

Step-by-step solution

Given lines are aligned & x-0 1 = y-0 -1 = z-0 0 and x-0 0 = y-0 1 = z-0 0 & Now, the angle = ⁻¹ ( a₁ a₂+b₁ b₂+c₁ c₂ a₁^2+b₁^2+c₁^2 a₂^2+b₂^2+c₂^2 ) & = ⁻¹ ( 1 0+(-1) 1+0 0 1^2+(-1)^2+0^2 0^2+1^2+0^2 ) & = ⁻¹ | -1 2 |[ for acute angle ] & = ⁻¹ ( 1 2 )= 4 aligned