Next Catriona Shearer puzzle.
Just One Fact
What’s the area of the square?
In contrast to the last one, this one borders on trivial. Add some lines:
AC is a diameter, so triangle ADC is right and triangles ABD and DBC are similar. AB is twice BD so BD is twice BC which is 1, so BD is 2, AB is 4, and the square’s area is 16.