Individual #trigonometry__trig  the mathematics of triangles and trigonometric functions
  >part of:  #pure_mathematics  the branches of mathematics that study and develop the principles of mathematics for their own sake rather than for their immediate usefulness
  >part:  #spherical_trigonometry__sphericaltrigonometry  the trigonometry of spherical triangles
  >part:  #triangulation.trigonometry  a trigonometric method of determining the position of a fixed point from the angles to it from two fixed points a known distance apart; useful in navigation

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