How do I know if this quadrilateral is cyclic?

Question

There are some pairs of angles that are equal to each other, but none of the values are known.

score 2 · Accepted Answer · answered Mar 04 '17 at 22:51

2

The qudrilaterial is cyclic because the two congruent angles $\angle DCA$ and $\angle DBA$ are inscribed angles from the chord $DA$.

Thus you can use Brahmagupta's formula for the area.

answered Mar 04 '17 at 22:51

Joffan

score 1 · Answer 2 · answered Mar 04 '17 at 22:34

1

A convex quadrilateral polygon in a plane is cyclic if, and only if, its opposite angles are supplementary.

answered Mar 04 '17 at 22:34

Wild Feather

2 Answers2