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Clarifying A GCSE Maths answer

Simple I think (I'm just crap at Maths).

If you were to draw a graph of x squared + y squared = 9, that would be a full circle going through '3' '3' '-3' '-3' on the graph right? So the radius of that circle would be 3?

Then you get this question: write down the equation of the tangent to the curve at the point (0,3), which would be three, wouldn't it? If the tangent is the side of the circle?

I'm sorry if this is confusing.
Yes, it would be a circle of radius 3.

You can't really say "the equation is 3". You'd need to say y = 3. If it was the tangent at the point (3,0), you'd say x = 3.
Reply 2
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Failed123
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Daniel Freedman
Yes, it would be a circle of radius 3.

You can't really say "the equation is 3". You'd need to say y = 3. If it was the tangent at the point (3,0), you'd say x = 3.

Okay thanks for clearing that up! Yes I mean y = 3 :p:
Reply 3
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Failed123
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Okay, I've never done these before, so if I get an equation like that again, would I just work out the square root of the number to work out the radius?
Reply 4
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Degausser
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As a rule, a circle with radius r and centre (a,b)

r2=(x−a)2+(y−b)2r^2 = (x-a)^2 + (y-b)^2
Is this edexcel gcse?
Reply 6
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Failed123
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jumblebumble
Is this edexcel gcse?

No AQA.

Keep in mind I'm terrible at Maths. I'm just going over past papers. I got the first half of the questions right, and then I got to this which I've never seen before :rolleyes:
Failed123
Okay, I've never done these before, so if I get an equation like that again, would I just work out the square root of the number to work out the radius?


Yes. x^2 + y^2 = r^2 is a circle that has its centre at (0,0) and a radius of r.
Reply 8
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Failed123
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Daniel Freedman
Yes. x^2 + y^2 = r^2 is a circle that has its centre at (0,0) and a radius of r.

Okay thanks! :p:

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