Originally Posted by

**Ciocolatta** Hi, I don't know how to approach this question, thanks in advance! =)

Let **v **be a unit vector and **c** a real number, and let **P** be the plane whose equation is **r.v **=** c** . Suppose also that $\displaystyle **r**<sub>0</sub>$ is a vector, and **A** the point whose position vector relative to the origin is $\displaystyle **r**<sub>0</sub>$.

a) Find in parametric vector form, the equation of the line **l** that is perpendicular to **P** and passes through **A**.

b) Let **B** be the point of intersection of the plane **P** and the line **l** in Part (a). Find a formula for the position vector of **B** relative to the origin, in t erms of $\displaystyle **r**<sub>0</sub>$, **v** and **c**.

=) yay