If in a right angled triangle ABC, hypotenuse AC = p, then what is AB . AC + BC . BA + CA . CB equal to?

The sine of the angle between vectors $$a = 2\widehat i - 6\widehat j - 3\widehat k$$ and $$b = 4\widehat i + 3\widehat j - \widehat k$$ is

What is the value of $$\lambda$$ for which the vectors $$3\widehat i + 4\widehat j - \widehat k$$ and $$ - 2\widehat i + \lambda \widehat j + 10\widehat k$$ are perpendicular?

Let $\vec{p}=\vec{a}-\vec{b},\vec{q}=\vec{a}+\vec{b}$. If $|\vec{a}|=|\vec{b}|=2$ and $\vec{a}\cdot \vec{b}=2$, then what is the value of $|\vec{p}\times \vec{q}|$?