Quandaries
and Queries 

Show that the peints A(2,0),B(6,6),C(1,7) and D(2,6) are concyclic. Also find its circum radius. 

Hi, You need to compute some angles: for a quadrangle to be cyclic the opposite angles must be supplementary. For R you can use the sine law in any of the triangles: 2R equals the ratio a/sin A (= the ratio of a side of a TRIANGLE to the sine of the opposite angle). Chris 

