noun
planar trigonometry
Technical term in mathematics, referring to trigonometry on a flat plane as opposed to spherical trigonometry.
平面三角法では、三角形の内角の和は180度である。
In planar trigonometry, the sum of the interior angles of a triangle is 180 degrees.
Spherical trigonometry, dealing with triangles on a sphere, as opposed to planar trigonometry.
Compound of 平面 (plane) + 三角法 (trigonometry).