Question

If vector `vec(A)=hat(i)+2hat(j)+4hat(k)` and `vec(B)=5hat(i)` represent the two sides of a triangle, then the third side of the triangle can have length equal to
A. `ssqrt(56)`
B. `sqrt(21)`
C. 5
D. 6

Answer 1

Correct Answer - A
`vec(A)+vec(B)+vec(C)=0`
So, `" " hat(i)+2hat(j)+4hat(k)+5hat(i)+vec(C)=0`
`vec(C)=-6hat(i)-2hat(j)-4hat(k)`
`|vec(C)|=sqrt(36+4+16)=sqrt(56)`
Hence A