Euclid — "An obtuse angle is an angle greater than a right angle."
An obtuse angle is an angle greater than a right angle.
An obtuse angle is an angle greater than a right angle.
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"If two triangles have two sides equal to two sides respectively, and have the angles contained by the equal straight lines equal, they will also have the base equal to the base, the triangle will be e…"
"To construct an equilateral triangle on a given finite straight line."
"Of quadrilateral figures, a square is that which is both equilateral and right-angled; an oblong that which is right-angled but not equilateral; a rhombus that which is equilateral but not right-angle…"
"And when the lines containing the angle are straight, the angle is called rectilineal."
"Sire, there is no royal road to geometry."
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