don't even know how to begin, does it involve factor/sum formulae?

angle ABC and angle ADC is 90 deg respectively. because AC is diameter.

angle BAD is 180deg-θ°. because of cyclic quadrilateral.....

how do i relate them and find AD?

sin x cos x = -(3/10)

then ....can i do this :

sin x = - (3/10) , cos x = - (3/10)

??? or i can only do this when it's equal to zero?

what i tried to do:

centre(0,0)

thus, i roughly know it would be something like (x^2)+(y^2).....

A(a,0)

B(0,b)

AB=2sqrt2

so..

sqrt{[(a-0)^2]+[(0-b)^2]}=2sqrt2

(a^2)+(b^2)=8

and then......i'm stuck ="=

how am i going to find the radius ...

and the question never mention about radius/diameter...