A⊥a', then a*a'=0, a * a' = 3x+4y = 0；; ②

The following results can be obtained from ① and ②: x=4/5, y =-3/5; Or x=-4/5, y = 3/5;

Therefore, the coordinates of the vector are (4/5, -3/5) or (-4/5, 3/5);

2. Let the vector c'=(x, y), then x? +y？ = 1; ①

C is parallel to c', then 5y-12x = 0; ②

From ① and ②, the results are: x=5/ 13, y =12/13; Or x=-5/ 13, y =-12/13;

Therefore, the coordinates of the vector are (5/ 13, 12/ 13) or (-5/ 12,-13);

3. Let the vector b'=(x, y), then x? +y？ = 1; ①

B is parallel to b', then y-(√ 3) x = 0; ②

The following results can be obtained from ① and ②: x= 1/2, y = (√ 3)/2; Or x=- 1/2, y =-(√ 3)/2;

Therefore, the coordinates of the vector are (1/2, (√3)/2) or (-1/2,-(√ 3)/2);

Have fun! I hope I can help you. . .