[질문] 세점-> P(0,0) , A(-1,0) , B(0,1)을지나는원의반지름의길이는? 답+풀이간략하게부?

(x-a)²+(y-b)²=r²에세점대입a²+b²=r²,(a+1)²+b²=r²,a²+(b+1)²=r²이나옴.연립해서풀면a=-1/2,b=-1/2.대입하면1/2=r²=>r=(루트)√2/2