@Psymon

Question

@Psymon

anonymous · Answer

attachment

nincompoop · Answer

@mayafrancis are you going to post all of your math homework or at least try to figure things out yourself also?

anonymous · Answer

its not homework i only post practices on here so ask questions first @nincompoop your dismissed i didn't ask for your input.

psymon · Answer

So first off the equation of a circle is 
$$(x-h)^{2}+(y-k)^{2}= r ^{2}   $$ The h is a movement left and right and the k is a movement up and down. So the h and the k tell us the coordinates of the center of a circle. So since the center of the circle is only at (0,0), we only have an x^2 + y^2 = r^2. As for the radius, r, this is the distance from themiddle of the circle to the edge of a circle. Now be careful, the distance from the center to the outer edge is r, NOT r^2. So always be mindful of that. You can tell what the radius is by just counting directly left, right, up or down from the middle. So for you, the distance from the center to the edge is just 1 unit. THis is r. And sense r = 1, r^2 is also just 1. Meaning the full equation ends up being
$$x ^{2} +y ^{2}=1  $$
Kinda make sense?

anonymous · Answer

and also @nincompoop ! i dont ask for the answers i ask questions so i can understand better as you saw in my last post so dont make it seem like im not trying to learn.

nincompoop · Answer

okay babe, continue

anonymous · Answer

@Psymon  so that equation is for any question deal with circles?

anonymous · Answer

dealing*

psymon · Answer

A better example to completely get the concept would be if the circle was not at the center and the radius was not 1. I think if we have a problem like that we can better show.

anonymous · Answer

ooo ok make sense:)

psymon · Answer

Mhm. Like for an example I could give this:

psymon · Answer

|dw:1378097449129:dw|

couldnt get the circle right, so had to hand draw xD So as mentioned, this is the formula for a circle:
$$(x-h)^{2}+(y-k)^{2}= r ^{2}$$
Now notice how I always put minus signs there. This means that the minus signs are supposed to be there and do not change. Because of this, if you ever see something liek (x+3)^2, this means the minus sign is gone. The only way for a minus sign to disappear is when you have something liek (x-(-3))^2 
Because of this, if you ever see (x+4)^2 or some + sign inthose parenthesis, the number paired with it is actually negative. So h represents a shift left and right and k represents a shift up and down. SO from the picture, can you tell the coordinates of the center?