STEP I 2016 Q6

Submitted by spacedino101 on Wed, 05/17/2017 - 12:51

Forums:

Discussion 2016-2017

Hi!

Referring to the mark scheme and my diagram

I can't get my head around how Y = b + beta k a

I get you go to B and then back down by a factor of a to Y but I'm not sure how you get to beta

Thanks

Is your confusion about why

Permalink Submitted by mr618 on Thu, 05/18/2017 - 08:50

Is your confusion about why the position vector of $Y$ has to be of the form $\mathbf{y}=\mathbf{b}+\beta k \mathbf{a}$ or how $\beta$ is obtained in the solutions?

If it's about the former, note that until $\beta$ is solved for, it is just an arbitrary parameter which can give the position vector of any point on the line $BC$ (on which $Y$ lies).