鈍角三角形 定義
An obtuse triangle (or obtuse angled triangle) is a triangle in which one of the interior angles is an obtuse angle (greater than π⁄2 radians or 90 degrees but less than π radians or 180 degrees). Obtuse triangles along with acute triangles are the two different types of oblique triangles (triangles that are not right triangles because they have no π⁄2 radians or 90 degree angles).
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“Acute and Obtuse Triangles.” Wikipedia, Wikimedia Foundation, 13 Mar. 2020, en.wikipedia.org/wiki/Acute_and_obtuse_triangles.
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