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# Circle geometry help watch

1. The points A(1,3), B(1,7), C(7,7) lie on the circle
a) draw a sketch
b) by considering the gradients on AB and BC show that AC is a diameter of the circle

for part (a) I've done something that resembles this: http://gyazo.com/7f2b0d1853cc5d8580ba2ea89eff17d2

and for part (b)
not sure how this will help me to show that AC is the diameter? I can see of the sketch that AC is the diameter but how do I use the gradients to show this?

Thanks!
2. (Original post by Secret.)
The points A(1,3), B(1,7), C(7,7) lie on the circle
a) draw a sketch
b) by considering the gradients on AB and BC show that AC is a diameter of the circle

for part (a) I've done something that resembles this: http://gyazo.com/7f2b0d1853cc5d8580ba2ea89eff17d2

and for part (b)
not sure how this will help me to show that AC is the diameter? I can see of the sketch that AC is the diameter but how do I use the gradients to show this?

Thanks!
Not sure if that question is right. But try considering the gradients OA and OC instead, where O is the origin of the circle
3. (Original post by 2710)
Not sure if that question is right. But try considering the gradients OA and OC instead, where O is the origin of the circle

OA = 3 and
OC = 1?
4. (Original post by Secret.)
OA = 3 and
OC = 1?
O is the centre of the circle, not (0,0). What is the centre of the circle?
5. (Original post by 2710)
O is the centre of the circle, not (0,0). What is the centre of the circle?

Do I work that out from the midpoint of AC?
6. (Original post by Secret.)
Do I work that out from the midpoint of AC?
You should have learnt this?

The centre of the circle is just (4,5). -1 times the number in the x bracket, and -1 times the number in the y bracket.
7. (Original post by 2710)
You should have learnt this?

The centre of the circle is just (4,5). -1 times the number in the x bracket, and -1 times the number in the y bracket.
Omg Yes! Sorry, I completely forgot the equation was even there!
But how come the question suggests working out the gradients of AB and AC?
8. (Original post by Secret.)
Omg Yes! Sorry, I completely forgot the equation was even there!
But how come the question suggests working out the gradients of AB and AC?
Is this on a paper? Or did your teacher give it to you. Maybe a typo or something? It cannot be AB because as u said, the gradient of that is infinity
9. (Original post by 2710)
Is this on a paper? Or did your teacher give it to you. Maybe a typo or something? It cannot be AB because as u said, the gradient of that is infinity
From a textbook
and I think what that means is it is a verticle straight line, which it is according to the diagram I made (the line x=1)
10. A straight vertical line is perpendicular to a straight horizontal line =_="

If you have a right triangle circumscribed by a circle, what is the triangle's hypotenuse with respect to the circle?
11. (Original post by aznkid66)
A straight vertical line is perpendicular to a straight horizontal line =_="

If you have a right triangle circumscribed by a circle, what is the triangle's hypotenuse with respect to the circle?
Oh yeh lol
12. (Original post by aznkid66)
A straight vertical line is perpendicular to a straight horizontal line =_="

If you have a right triangle circumscribed by a circle, what is the triangle's hypotenuse with respect to the circle?
The diameter? I said that above but I thought it wanted working out using the gradients of AB and AC
13. (Original post by Secret.)
The diameter? I said that above but I thought it wanted working out using the gradients of AB and AC
One of the circle theorems states that the angle formed by a triangle in a circle when the hypotenuse is the diameter is a right angle. show that the two lines are perpendicular and that the hypotenuse passes through the centre of the circle.

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Updated: March 25, 2013
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