The Gamma Trianguli sector was a region of space in the Alpha Quadrant. Named after the star Gamma Trianguli, this sector contained Archer's Planet and Gamma Trianguli VI. (TOS: "The Apple"; ENT: "In a Mirror, Darkly, Part II", display graphic)
The Star Trek: Enterprise fourth season episode "In a Mirror, Darkly, Part II" revealed this sector reference, as well as the planet's name, in text appearing in Jonathan Archer's personnel file. The original production artwork can be viewed at MikeSussman.net.
"The Explored Galaxy" was a map of charted space in the Alpha Quadrant. Gamma Trianguli was located between the Tholian Assembly
. Both locations were identified in DS9
: "The Search, Part II
", "Call to Arms
" as being located in this quadrant. This star chart, first seen chronologically in Star Trek VI: The Undiscovered Country, was also seen in several Star Trek: The Next Generation and Star Trek: Deep Space Nine episodes set in the 24th century, from the year 2364 to 2370. These were: TNG: "Conspiracy", "The Measure Of A Man", "The Emissary", "The Mind's Eye", "The Game" and DS9: "In the Hands of the Prophets", "Cardassians".