Semicircular Protractor
A 6 inches diameter protractor to measure angles to half degrees, made of brass or German silver. They…
Quadrilateral With Diagonals
Illustration to show that if the diagonals of a quadrilateral bisect each other, the figure is a parallelogram.
Ravelin
A detached triangular work in fortification, with two embankments which form a projecting angle. In…
Rectangle With Diagonals
Illustration to show that if the diagonals of a parallelogram are equal, the figure is a rectangle.
Reflected Motion
"Suppose a, b, to be a marble floor, and c, to be an ivory ball, which has be thrown towards the floor…
Airplane Rudder and Elevator
A propeller airplane with rudder, elevator, and ailerons. The rudder stabilizes the plane vertical,…
Right Angles Inscribed in Semicircle Proof
Illustration of a circle used to prove "Any angle inscribed in a semicircle is a right angle."
Shoe Block
"Nautically, a block with two sheaves, whose axes are at right angles to each other, used for the buntlines…
Polyhedral Angle in a Sphere
Illustration of a sphere with a polyhedral angle whose vertex is at the center of the sphere and whose…
Measure of a Spherical Angle
Diagram used to prove the theorem: "A spherical angle is measured by the arc of a great circle described…
Side Comparison of Spherical Triangle
Diagram used to prove the theorem: "In a spherical triangle, the greater side is opposite the greater…
Survey of Lake Front in Chicago
Illustration showing a survey on the lake front in Chicago with distances and angle measures shown.
2 Triangles Theorem
Illustration used to prove that "If two triangles have two sides of one equal respectively to two sides…
2 Triangles Theorem
Illustration used to prove that "If two triangles have two sides of one equal respectively to two sides…
Sides of Triangle Theorem
Illustration used to prove that "If two sides of a triangle are unequal, the angle opposite the greater…
Sides of Triangle Theorem
Illustration used to prove that "The sum of any two sides of a triangle is greater than the third side."
Leaning Tower
Illustration of a leaning tower with a perpendicular drawn from the top of the tower to the ground to…
2 Lines Cut By A Transversal
Illustration of two straight lines cut by a transversal. The 8 angles formed are labeled.
2 Lines Cut By A Transversal
Illustration of two straight lines, AB and CD, cut by a transversal EF.
Using Proportions To Find Heights of Trees
Triangle diagram for measuring heights of trees using proportions.
Using Proportions To Find Heights of Trees
Triangle diagram for measuring heights of trees using proportions
Acute Triangle
Illustration showing an acute triangle (one that has all three angles that are acute).
Altitudes Drawn from Base Angles of Isosceles Triangles
Illustration to show altitudes drawn from base angles of an isosceles triangle.
Angle Bisectors In A Triangle
Illustration used to prove "The bisectors of the angles of a triangle are concurrent in a point which…
Triangle With Bisector and Perpendicular From Vertex Drawn
Illustration to show the bisector of the vertical angle of a triangle makes with the perpendicular from…
Bisector of an Exterior Angle of an Isosceles Triangle
Illustration to show that the bisector of an exterior angle of an isosceles triangle, formed by producing…
Triangle With Bisectors of Base Angles
Illustration to show if the bisector of the base angles of a triangle are drawn, and through their point…
Triangle With Bisectors of Vertical Angles
Illustration to show the bisector of the vertical angle A of a triangle ABC, and the bisectors of the…