Please help, not sure how to do this. I did everything else (i did the standard form already, just need the last part which is the radius). don't have a clue on how to get the radius. thank you!

1) FIND THE STANDARD FORM OF THE EQUATION OF THE CIRCLE W/ CENTER (-1,3) AND TANGENT TO THE LINE Y=1

*the standard form of the equation of this circle is:

Question

Please help, not sure how to do this. I did everything else (i did the standard form already, just need the last part which is the radius). don't have a clue on how to get the radius. thank you!

1) FIND THE STANDARD FORM OF THE EQUATION OF THE CIRCLE W/ CENTER (-1,3) AND TANGENT TO THE LINE Y=1

*the standard form of the equation of this circle is:

anonymous · Answer

Ok knowing that the circle must be tangent to the line y=1, we have to determine what the radius must be. Tangent means that it only touched the circle in one place. Since our circle has a center of (-1,3) it is in the second quadrant correct? The line y=1 is a horizontal line that goes through on meaning it much touch the very bottom of the cirlc or the point (-1,1).

This means our radius must be 2

therefore our equation should be:

$$(x+1)^2+(y-3)^2=4$$

anonymous · Answer

sorry its late that had many spelling mistakes but the picture is still clear i believe. ha ha

anonymous · Answer

center of circle (-1,3) and radius is ____?

standard form (x+1)^2+(y-3)^2= ______?...did i pretty much get that part?

anonymous · Answer

yup correct

anonymous · Answer

oh hi dichiaraj! thank you...i was trying to figure out the 2....i see it. thank you.  you are indeed a lifesaver. i saw dumbcow earlier but disappeared...saying hello anyway. thank you all for your help.

anonymous · Answer

yea no problem.

dumbcow · Answer

haha, yeah i saw your question
agree with answer above :)

only thing i could add is the line from tangent point to center is always perpendicular to tangent line
in this case tangent line is horizontal, so perpendicular line is vertical line through center
they meet at (-1,1) which is length 2 from center...radius=2

anonymous · Answer

Yes that is important to point out good addition.

anonymous · Answer

that's a real good one. the first one i did before this one showed horizontal line. i'm still trying to figure out the new calculator, believe it or not =) and well, it's late....i'm ususally doing more than 20, 30 problems in a day and after a while i get stuck w/ something...lol. but thank you also dumbcow...that should be "smart"cow! really appreciate your help! same to you dichiaraj!