Coordinate Geometry II TRIANGLES

aek

The question is in the attached picture.

i can't seem to find a relevant formula and when i do i can't get a suitable answer, if some one can help, i'll highly appreciate it. Thanks in advance.

Attached Thumbnails

 

Pseudo Statistic

a) It wants the equation of SD, as it looks to me...
You see that it hits D right in the middle of AC, so find the midpoint of AC.
Then, you have the co-ordinate S(0,-2) and that midpoint, do y-y1 = m(x-x1)

b) ... Should be x - y = -2 according to the graph given.

c) ...the co-ordinates are already given?

d) Similar method to a)

e) Pretty much find the distance between each of these points and S and prove that to be the radius of the circle. (radius should be square root 40)