This figure represents an apparatus frequently employed for illustrating some of the consequences of…

Illustration used to show that "If two tangents are drawn from any given point to a circle, those tangents…

Illustration used to show that "A tangent to a circle is perpendicular to the radius drawn to the point…

An illustration used to show how the area of a circle is calculated. Area is equal to the product of…

Illustration used to show that "The diameter perpendicular to a chord bisects the chord and also its…

Illustration used to show that "In equal circles, or in the same circle, if two chords are equal, they…

Illustration used to show that "In equal circles, or in the same circle, if two chords are equal, they…

Illustration used to show that "In equal circles, or in the same circle, if two chords are unequal,…

Illustration used to show that "In equal circles, or in the same circle, if two chords are unequal,…

Illustration used to show that "In equal circles, or in the same circle, if two chords are unequal,…

Illustration used to prove the corollary that "Two lines perpendicular respectively to two intersecting…

Illustration used to prove the corollary that "From a point outside a line there exists only one perpendicular…

An illustration showing a model of a circle with intersecting chords that illustrates the following…

An illustration showing a model of a triangle that illustrates the following relationship: a:c = d:(b…

An illustration showing a quadrilateral model that illustrates the following relationships: a:b = c:d,…

An illustration showing a model that illustrates the following relationships: a:b = c:d, ad = bc. Product…

An illustration showing a model that illustrates the following relationships: a:b = c:b, ab = c²,…

An illustration showing a model that illustrates the following relationship: A:B = a:b.

An illustration showing a model that illustrates the following relationships: a:x = x:a - x, x = √(a²…

An illustration showing a model of 2 circles with tangent lines, diameters, and radii that illustrates…

An illustration showing a model of 2 circles with tangent lines, diameters, and radii that illustrates…

An illustration showing a model of a circle with an exterior angle formed between a tangent and a secant…

An illustration showing a model of a circle with angles formed between tangents and secants that illustrates…

"If from the foot of a perpendicular to a plane a straight line is drawn at right angles to any line…

"All the perpendiculars to a straight line at the same point lie in a plane perpendicular to the line."

"If a straight line is perpendicular to each of two straight lines at their point of intersection it…

"If one of two parallels is perpendicular to a plane, the other is also."

Illustration used to prove "Two angles whose sides are perpendicular each to each are either equal or…

Illustration used to prove the Pythagorean Theorem, according to Euclid. A perpendicular is drawn from…

Illustration used to prove "An exterior angle of a triangle is equal to the sum of the two remote interior…

Illustration that can be used to prove the Pythagorean Theorem, the sum of the squares of the legs is…

Illustration that can be used to prove the Pythagorean Theorem, the sum of the squares of the legs is…

A visual illustration used to prove the Pythagorean Theorem by rearrangement. When the 4 identical triangles…

Illustration used to prove "If the sides of any polygon are prolonged in succession one way, no two…

Illustration used to prove "The sum of all the angles of any polygon is twice as many right angles as…

"A proof-plane may be made by cementing a bronze cent or a disk of gilt paper to a thin insulating handle,…

Illustration used to prove that "If two triangles have two sides of one equal respectively to two sides…

Illustration used to prove that "If two triangles have two sides of one equal respectively to two sides…

Illustration used to prove that "If one side of a triangle is prolonged, the exterior angle formed is…

Illustration used to prove that "If two straight lines are parallel to a third straight line, they are…

Illustration used to prove that "If two sides of a triangle are unequal, the angle opposite the greater…

Illustration used to prove that "The sum of any two sides of a triangle is greater than the third side."

Illustration of triangle ABC with BE extended through the triangle at point D. Segment AB is equal to…