C4 vector question

https://983c9f06eb1f75af6e83364e092b06f1cb5c4277.googledrive.com/host/0B1ZiqBksUHNYZzd2VHZlOXdqZlE/January%202010%20QP%20-%20C4%20OCR.pdf

For question 2ii we have to find an angle for ABC. The markscheme says AB.BC. However, when I do normal vector questions, I do the vectors coming out of the angle, i.e BA.BC. Why is this one different or do I have the wrong approach?
Thank you

Can you pass me the mark scheme?

https://983c9f06eb1f75af6e83364e092b06f1cb5c4277.googledrive.com/host/0B1ZiqBksUHNYZzd2VHZlOXdqZlE/January%202010%20QP%20-%20C4%20OCR.pdf

For question 2ii we have to find an angle for ABC. The markscheme says AB.BC. However, when I do normal vector questions, I do the vectors coming out of the angle, i.e BA.BC. Why is this one different or do I have the wrong approach?
Thank you

I have checked the two methods and both are correct.

Thanjks so much, I just did an error in my working

https://983c9f06eb1f75af6e83364e092b06f1cb5c4277.googledrive.com/host/0B1ZiqBksUHNYZzd2VHZlOXdqZlE/January%202010%20QP%20-%20C4%20OCR.pdf

For question 2ii we have to find an angle for ABC. The markscheme says AB.BC. However, when I do normal vector questions, I do the vectors coming out of the angle, i.e BA.BC. Why is this one different or do I have the wrong approach?
Thank you

The method you use is the correct one for ALL cases. However, when the angle between 2 lines is 90 or 180 degrees, then options to use the head-to-tail vector approach becomes correct as well. I've attached an image to to show you what I mean.