Correct option is A
1. Convert to symmetric form:31x=31y=−21zand21x=−1y=−31z2. Identify direction vectors:a=(31,31,−21),b=(21,−1,−31)3. Compute dot product:a⋅b=(31×21)+(31×−1)+(−21×−31)=61−31+61=04. Calculate magnitudes:∣a∣=(31)2+(31)2+(−21)2=91+91+41=3617=617∣b∣=(21)2+(−1)2+(−31)2=41+1+91=3649=675. Find angle:cosθ=∣a∣∣b∣a⋅b=617×670=0θ=cos−1(0)=90∘Final Answer:90∘