You are Here: Home >< Maths

# AQA core 1, circles qus watch

1. How would you answer these two:

1.) AB is a chord of a circle where A is at (1,3) and B is at (4,4). The tangent to the circle at A is the line y=2x + 1.
Find the equation of the circle.

and 2.) Line y=-2 is a tangent to the circle x^2 + y^2 + 2x - 4y = 11.
Find the co-ordinates of the point of contact.
2. 1) Tangent at A is perpendicular to the radius (so what is the line of equation which is includes the radius?) and perpendicular bisector of the chord AB goes through the centre. How can you use that information to find the centre of the circle ?

I have no idea whether this is the best way, probably others.

2) Sub in y = -2 into the circle and find x.
3. (Original post by insparato)
1) Tangent at A is perpendicular to the radius (so what is the line of equation which is includes the radius?) and perpendicular bisector of the chord AB goes through the centre. How can you use that information to find the centre of the circle ?

I have no idea whether this is the best way, probably others.

2) Sub in y = -2 into the circle and find x.
I would do A that way and form a triangle to work out radius/centre.
4. I got it in the end but thanks you were helpful

### Related university courses

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 18, 2010
Today on TSR

How do you think you'll do?

### University open days

Wed, 25 Jul '18
2. University of Buckingham
Wed, 25 Jul '18
3. Bournemouth University
Wed, 1 Aug '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