If $\vec A = 2\hat i + \hat j - \hat k,\,\vec B = \hat i + 2\hat j + 3\hat k$ and $\vec C = 6\hat i - 2j - 6\hat k$ then the angle between $(\vec A + \vec B)$ and $\vec C$ wil be ....... $^o$

$\vec{A}$ is a vector quantity such that $|\vec{A}|=$ nonzero constant. Which of the following expressions is true for $\vec{A}$ $?$

The angle between $(\overrightarrow A - \overrightarrow B )$ and $(\overrightarrow A \times \overrightarrow B )$ is $(\overrightarrow{ A } \neq \overrightarrow{ B })$

What is the product of two vectors if they are parallel or antiparallel ? 

A vector $\overrightarrow A $ points vertically upward and $\overrightarrow B $points towards north. The vector product $\overrightarrow A \times \overrightarrow B $ is

Vectors $a \hat{i}+b \hat{j}+\hat{k}$ and $2 \hat{i}-3 \hat{j}+4 \hat{k}$ are perpendicular to each other when $3 a+2 b=7$, the ratio of a to $b$ is $\frac{x}{2}$. The value of $x$ is $..............$