Circle geometry problem with tangents and intersecting chords, calculating unknown angles.
Geometry problem involving a circle with center O, tangents at points A and C meeting at T, and angle ATC = 40°. The diagram shows chords AD and CE intersecting at F, with angles labeled x, y, and z to be determined. A calculation for x is shown: 360° - 90° - 90° - 40° = 140° (sum of angles).