Question 1070322
The point (3,-4) is in quadrant 4, for the lower half of the circle.

{{{y=-(25-x^2)^(1/2)}}}


{{{dy/dx=x/sqrt(25-x^2)}}}, skipping the steps here.

At x=3, {{{dy/dx=3/4}}}, the slope for the line on the circle at point (3,-4).
That tangent line:  {{{highlight(y+4=(3/4)(x-3))}}}.


(b)
Can you do this part?