Circles Q

Help I don’t get how I would know for part 7 b that it passes through origin and touches the x axis but not the y…
I don’t understand part 7 b at all plz help, I get the rest

(edited 1 year ago)

Reply 1

mqb2766

Im guessing you not sketched it yourself (centre and distances to axes)?

Reply 2

Alevelhelp.1

Original post by mqb2766

Im guessing you not sketched it yourself (centre and distances to axes)?

I have but it just touches the X and Y axis

Reply 3

mqb2766

Not sure what you mean by that. A single radius will not touch both axes. Upload your sketch(es) if necessary?

(edited 1 year ago)

Reply 4

the bear

since the centre is at (3, 4) if the circle touches the y axis exactly once ( ie the y axis is a tangent ) then the radius would be 3, and it would not reach the x axis.

as the radius increases from 3 to 4 the circle crosses the y axis twice, until when it reaches 4 it has a third intersection at the x axis.

as the radius increases from 4 to 5 there are 4 intersections, 2 on each axis. when the radius reaches 5 then it goes back to 3, as the smaller y intersection and the smaller x intersection are at the same point, namely the origin