In triangle ABC (Fig 10.18), which of the following is not true:

(a)

(b)

(c)

(d)

We know by triangle law of vectors,

…………..(1)

Therefore,

Hence (B) is true.

We know that

Putting in eq(1), we get

…….(2)

Hence (A) is also true.

Now,

Putting in eq(2)

Hence (D) is correct.

We are asked the option which is not true.

Therefore, the correct option is (C).