The values of $x$ and $y$ for which vectors $A =(6 \hat{ i }+x \hat{ j }-2 \hat{ k })$ and $B =(5 \hat{ i }+6 \hat{ j }-y \hat{ k })$ may be parallel are

Projection of vector $\vec A$ on $\vec B$ is

Three particles ${P}, {Q}$ and ${R}$ are moving along the vectors ${A}=\hat{{i}}+\hat{{j}}, {B}=\hat{{j}}+\hat{{k}}$ and ${C}=-\hat{{i}}+\hat{{j}}$ respectively. They strike on a point and start to move in different directions. Now particle $P$ is moving normal to the plane which contains vector $\vec{A}$ and $\vec{B} .$ Similarly particle $Q$ is moving normal to the plane which contains vector $\vec{A}$ and $\vec{C} .$ The angle between the direction of motion of $P$ and $Q$ is $\cos ^{-1}\left(\frac{1}{\sqrt{x}}\right)$. Then the value of $x$ is ...... .

The angle between the vectors $(\hat i + \hat j)$ and $(\hat j + \hat k)$ is ....... $^o$

A vector has magnitude same as that of $\overrightarrow{\mathrm{A}}-=3 \hat{\mathrm{j}}+4 \hat{\mathrm{j}}$ and is parallel to $\overrightarrow{\mathrm{B}}=4 \hat{\mathrm{i}}+3 \hat{\mathrm{j}}$. The $\mathrm{x}$ and $y$ components of this vector in first quadrant are $\mathrm{x}$ and $3$ respectively where  $X$=_____.