Question

If a circle touches X-axis then

$g {}^{2} = c$
HOW?? PLEASE EXPLAIN (11TH)​

Answer 1

if circle touch x axis

then as line parallel to y axis would be normal which will pass through centre so its y coordinate becomes radius

As y cordinate is -f

radius = √g^2 + f^2 - c

So |-f| = √g^2 + f^2 - c

squaring

f^2 = g^2 + f^2 - c

g^2 - c= 0

g^2 = c