Vertical Angle Theorem
When two straight lines intersect at a point, four angles are made. The non-adjacent angles are called vertical or opposite or vertically opposite angles. Also, each pair of adjacent angles forms a straight line and the two angles are supplementary. Since either of a pair of vertical angles is supplementary to either of the adjacent angles, the vertical angles are equal in measure. Eudemus of Rhodes attributed the proof of this theorem to Thales of Miletus. According to a historical Note, when Thales visited Egypt, he observed that whenever the Egyptians drew two intersecting lines, they would measure the vertical angles to make sure that they were equal. Thales concluded that one could prove that all vertical angles are equal if one accepted some general notions such as: all straight angles are equal, equals added to equals are equal, and equals subtracted from equals are equal.
Read more about this topic: Vertical Angles
Famous quotes containing the words vertical, angle and/or theorem:
“I tell you, hopeless grief is passionless;
That only men incredulous of despair,
Half-taught in anguish, through the midnight air
Beat upward to God’s throne in loud access
Of shrieking and reproach. Full desertness,
In souls as countries, lieth silent-bare
Under the blanching, vertical eye-glare
Of the absolute Heavens.”
—Elizabeth Barrett Browning (1806–1861)
“Modesty is the only sure bait when you angle for praise.”
—Philip Dormer Stanhope, 4th Earl Chesterfield (1694–1773)
“To insure the adoration of a theorem for any length of time, faith is not enough, a police force is needed as well.”
—Albert Camus (1913–1960)