Triangles & Congruence Flashcards

What is a triangle?

Answer: A polygon with three sides and three vertices

A triangle is a fundamental polygon defined by three sides and three vertices (corners). It is the simplest polygon and its interior angles always sum to 180 degrees. Triangles are extensively used in geometry, engineering, and architecture due to their rigidity and versatility.

What does it mean for two triangles to be congruent?

Answer: They have equal corresponding sides and angles

For two triangles to be congruent, they must have exactly the same size and shape. This means that all their corresponding sides must be equal in length, and all their corresponding angles must be equal in measure. If two triangles are congruent, one can be perfectly superimposed onto the other.

Which is a method for proving triangle congruence?

Answer: SAS

SAS (Side-Angle-Side) is a valid method for proving triangle congruence. This postulate states that if two sides and the included angle of one triangle are congruent to two sides and the included angle of another triangle, then the triangles are congruent. This ensures that the triangles have identical shape and size.

What is the sum of interior angles in a triangle?

Answer: 180 degrees

In Euclidean geometry, the sum of the interior angles in any triangle always equals 180 degrees. This is a fundamental theorem that applies to all types of triangles, regardless of their side lengths or individual angle measures. This property is crucial for solving many geometric problems.

Which triangle has all sides equal?

Answer: Equilateral triangle

An equilateral triangle is a special type of triangle where all three sides are equal in length. As a result of having equal sides, all three interior angles are also equal, each measuring 60 degrees. This makes it a highly symmetrical and balanced geometric figure.

Which triangle has two equal sides?

Answer: Isosceles triangle

An isosceles triangle is defined by having at least two sides of equal length. Consequently, the angles opposite these two equal sides, known as the base angles, are also equal in measure. This property gives isosceles triangles a distinct symmetrical characteristic.

What does the term 'scalene' mean for triangles?

Answer: All sides and angles are different

A scalene triangle is defined by having all three of its sides of different lengths. Consequently, all three interior angles will also be different from each other. This distinguishes it from equilateral triangles (all sides equal) and isosceles triangles (two sides equal).

Which triangle has one angle measuring 90 degrees?

Answer: Right triangle

A right triangle is specifically characterized by having one of its interior angles measure exactly 90 degrees. This 90-degree angle is often indicated by a small square symbol at its vertex. The side opposite the right angle is called the hypotenuse, and it is always the longest side.

Which triangle has one angle greater than 90 degrees?

Answer: Obtuse triangle

An obtuse triangle is identified by having one interior angle that measures greater than 90 degrees. Since the sum of angles in any triangle is 180 degrees, an obtuse triangle can only have one such angle. The other two angles must therefore be acute (less than 90 degrees).