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acute triangle

a triangle whose interior angles are all acute

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auxiliary line

line (or ray or segment) added to a diagram to help in a proof

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base angles

the angles whose vertices are the endpoints of the base of the triangle

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congruence transformation

Transformation that changes the position of the figure without changing its size or shape. Rotation, Translation or Reflection.

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congruent polygons

polygons with same size and shape

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coordinate proof

A proof involving placing geometric figures in a coordinate plane.

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corollary

(logic) an inference that follows directly from the proof of another proposition

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corresponding parts

Sides or angles that occupy the same relative positions in similar polygons.

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equiangular triangle

A triangle with 3 congruent angles

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equilateral triangle

a triangle with three congruent sides

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exterior angle

An angle formed by one side of a polygon and the extension of an adjacent side

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flow proof

a type of proof that uses arrows to show flow of a logical argument statements are connected by arrows to show how each statement comes before it. and each reason is written below the statement it justifies

###
included angle

An angle created by two adjacent sides

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included side

the common side of two consecutive angles of a polygon

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isosceles triangle

a triangle with two equal sides

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obtuse triangle

a triangle that contains an obtuse interior angle

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reflection

A transformation that "flips" a figure over a mirror or reflection line.

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remote interior angles

the two nonadjacent interior angles corresponding to each exterior ange of a triangle

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right triangle

a triangle with one right angle

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rotation

(mathematics) a transformation in which the coordinate axes are rotated by a fixed angle about the origin

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scalene triangle

a triangle with no two sides of equal length

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translation

(mathematics) a transformation in which the origin of the coordinate system is moved to another position but the direction of each axis remains the same

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vertex angle

the angle in a triangle opposite the base

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