You are Here: Home >< Maths

# A vector perpendicular to a circle watch

Announcements
1. Hello all,
just came across a question that sort of confused me since I haven't really seen anything like it before. Anyway here it is.
"Given that a = 2sinθi + ( 1-sinθ )j, find the value of the acute angle θ, so that a is perpendicular to the line x+y=1."
I have tried a few approaches but none of the seem to work, its probably not too difficult once you get it, but would like some help if anyone has some time to spare.
Thanks!
2. The given line can be written as y=1-x so a line perpendicular to this would have gradient (-1)/(-1)=1. Therefore, you want a to be parallel to the y=x line. For this to be the case, you would have 2sin=1-sinθ, which you can then solve for theta.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: January 15, 2010
Today on TSR

### University open days

1. Norwich University of the Arts
Fri, 28 Sep '18
2. Edge Hill University
Faculty of Health and Social Care Undergraduate
Sat, 29 Sep '18
3. Birmingham City University
Sat, 29 Sep '18
Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams