Given vector A = 3i + 4j – 5k
Its magnitude is,
|A| = √(32 + 42 + (-5)2)
= √(9 + 16 + 25)
= √50
= 5√2
The unit vector in the direction of the given vector is,
^A = A/|A|
= (3i + 4j – 5k) / (5√2)
Answer: A

Hence the unit vector is (3/5√2) i + (4/5√2) j – (5/5√2) k.