Given l1:3x−2=−2y+1=0z−2
l2:1x−1=2αy+23=2z+5
l3:−3x−1=−2y−21=4z−0
Since l1 is perpendicular to l2, so 131+4α2+4∣3−α+0∣=0⇒α=3
Now for angle between l2 & l3,
cosθ=1+4α2+49+4+16∣1×(−3)+(−2)(2α)+2×4∣
cosθ=5+4α229∣−3−α+8∣
Putting α=3
cosθ=429292=294
θ=cos−1(294)⇒θ=sec−1(429)