Question
a) Let c1 = 1 and c2 = 2, find c3 which makes 
coplanar.
b) If c2 = –1 and c3 = 1, show that no value of c1 can make 
coplanar.
Solution
then,
a) c1 = 1 and c2 = 2,
For vectors to be coplanar scalar triple product should be equal to zero.
b) c2 = –1 and c3 = 1
