The vector (s) which is/are coplanar with vectors $${\widehat i + \widehat j + 2\widehat k}$$ and $${\widehat i + 2\widehat j + \widehat k,}$$ and perpendicular to the vector $${\widehat i + \widehat j + \widehat k}$$ is/are

Let $${\overrightarrow A }$$ be vector parallel to line of intersection of planes $${P_1}$$ and $${P_2}.$$ Planes $${P_1}$$ is parallel to the vectors $$2\widehat j + 3\widehat k$$ and $$4\widehat j - 3\widehat k$$ and that $${P_2}$$ is parallel to $$\widehat j - \widehat k$$ and $$3\widehat i + 3\widehat j,$$ then the angle between vector $${\overrightarrow A }$$ and a given vector $$2\widehat i + \widehat j - 2\widehat k$$ is

Let $$a$$ and $$b$$ two non-collinear unit vectors. If $$u = a - \left( {a\,.\,b} \right)\,b$$ and $$v = a \times b,$$ then $$\left| v \right|$$ is

Which of the following expressions are meaningful?