en.wikipedia.org/wiki/Transversal_(geometry)

In geometry, a transversal is a line that passes through two lines in the same
plane at two ... cuts two parallel lines at right angles is called a perpendicular
transversal. ... If the two angles o...

www.mathopenref.com/anglesvertical.html

As can be seen from the figure above, when two lines intersect, four angles are
formed. Each opposite pair are called vertical angles and are always congruent.

www.mathplanet.com/education/pre-algebra/introducing-geometry/angles-and-parallel-lines

Vertical angles are always congruent, which means that they are equal. ... that
are on the outside of the two parallel lines like 1 and 6 are called exterior angles.

www.mathsisfun.com/geometry/congruent-angles.html

Congruent Angles have the same angle (in degrees or radians). That is all. ... the
same angle. Congruent - why such a funny word that basically means "equal"?

www.reference.com/math/vertical-angles-congruent-e2e1fa473d7df470

In mathematics, vertical angles are always congruent. Vertical angles are the
angles ... when two lines intersect. They are called vertical because the angles
share.

www.math.com/school/subject3/lessons/S3U1L5DP.html

Vertical angles are pairs of angles formed by two intersecting lines. ... in four
corresponding pairs that have the same measure, so therefore are congruent. ...
area between the two lines that are cut by the transversal, are called interior
angles.

www.wyzant.com/resources/lessons/math/geometry/lines_and_angles/pairs_of_angles

Another special pair of angles is called supplementary angles. One angle is said
to be the ... Vertical angles always have equal measures. ?JKL and ?MKN are ...

www.khanacademy.org/math/geometry-home/geometry-angles/geometry-vert-comp-supp/v/proof-vertical-angles-are-equal

Proving that vertical angles are equal. ... Vertical angles are congruent proof ... --
so, angle DBA-- then I'd prove that vertical angles are always going to be equal, ...

www.freemathhelp.com/feliz-special-angles.html

Certain types of angles, known as complementary, supplementary, and ... We
called the smaller angle x, so the larger one must be 14x because we know it's
14 ... Vertical angles are opposite pairs of congruent (or equal) angles that are
made ...

proofsfromthebook.com/2013/01/19/proof-that-vertical-angles-are-congruent/

Jan 19, 2013 ... A pair of angles whose sides form two lines is called vertical angles. In the figure
below, angles 1 and 3 are vertical angles since their sides ...