Ex. 89. A quadrilateral $A B C D$ is inscribed in a circle, the lengths of whose sides are given: $A B=1, B C=2, C D=3, D A=4$. Find its area $and$ the radius of the circumscribed circle.
Ex. 89. $S=2 \sqrt{6}, R=\frac{\sqrt{7} \cdot 55}{4 \sqrt{6}}$.