Geometry Glossary - T  

Tangent:

in a right triangle, the ratio of the sine of an angle and the cosine of the same angle

Tangent to a circle:

a line that touches the circle in exactly one point

Theorem:

a statement that has been proven; the proof shows the statement follows logically from axioms, definitions, and/or other theorems

Transformation:

a geometric mapping in which each point has exactly one image point and each image point has exactly one pre-image point; that is, there is a one-to-one correspondence between points and their images

Transformational proof:

a proof of a geometric concept using translations, reflections, rotations, and dilations (stretches and shrinks)

Translation (of geometric figures; of vectors):

in geometry, this is a composite of two reflections over two parallel lines, also called a slide; with vectors, this means that each component of the vector has the same component added to it, sliding the vector to new position parallel to the original vector

Transversal:

a segment or line that intersects two or more lines

Trapezoid:

a quadrilateral with exactly two parallel noncongruent sides

 

Triangle:

• the union of three noncollinear points and the segments that connect them

Two-column proof:

this format is most often used to prove theorems in geometry; the proof has given statement(s), a to prove statement, and usually a diagram; below these are two columns in which one column lists statements, connecting the given to what is to be proven and the other column lists reasons for the statements (also called a T-column proof)

Two-Dimensional:

existing on a plane; having length and width, but no depth