 ### Path of Projectile

Illustration modeling the path of a projectile. ### Angles With Perpendicular Sides Are Equal or Supplementary Proof

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

Illustration used to prove "An exterior angle of a triangle is equal to the sum of the two remote interior… ### Sum of Exterior Angles of a Polygon Proof

Illustration used to prove "If the sides of any polygon are prolonged in succession one way, no two… ### Sum of Interior Angles of a Polygon Proof

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

A math tool used for measuring angles on blueprints. ### Semicircular Protractor

A 6 inches diameter protractor to measure angles to half degrees, made of brass or German silver. They… ### Triangular Pyramids for Volume

Illustration showing that the volume of 2 triangular pyramids, having the same trihedral angle of the… ### Triangles and Sectors in Quadrant I

Illustration of an angle &alpha with the vertex at the center, O, of a circle with radius OB. AC and… ### Triangle in Quadrant I

Illustration of an angle &alpha with the terminal side used to draw a triangle in quadrant I. ### Triangle in Quadrant II

Illustration of an angle with the terminal side used to draw a triangle in quadrant II. ### Printers Quoin

A printers quoin is a device for locking up or fastening type in chases or galleys. ### Ravelin

A detached triangular work in fortification, with two embankments which form a projecting angle. In… ### Rectangle

Rectangle with angles labeled. Parallelogram with right angles. ### Redans

In field fortification, the simplest kind of work employed, consisting of two parapets of earth raised… ### Law of Reflected Motion

"The angle, ABD, included between the direction of the moving body before it strikes the reflecting… ### Reflected Motion

"... if a ball be thrown from F against the surface B C so as to strike it perpendicularly at A, it… ### Reflection of Light

"Angle of incidence equals angle of reflection." —Croft 1917 ### Reflection of Light

"The ray a, c, is the ray of incidence, and that from c, to d, is the ray or reflection. The angles… ### Relationships In A Right Triangle

Illustration used to show "If one acute angle of a right triangle is double the other, the hypotenuse… ### Roof With 30 degree Inclination for Trigonometry Triangle Problems

Roof with a slope of 30 degrees. Angle theta is the inclination to the horizontal of the line AB, drawn… ### Airplane Rudder and Elevator

A propeller airplane with rudder, elevator, and ailerons. The rudder stabilizes the plane vertical,… ### Circle with Secant

A secant is "a line which cuts a figure in any way. Specifically, in trigonometry, a line from the center… ### Shoe Block

"Nautically, a block with two sheaves, whose axes are at right angles to each other, used for the buntlines… ### Law of Sines

Illustration two types of triangles that can be used to model the law of sines. "In a plane triangle… ### Napier's Right Spherical Triangle

Illustration of a right spherical triangle and the five circular parts placed in the sectors of a circle… ### Relationships In A Spherical Triangle

Illustration used, with the law of sines, to find the relation between two sides of a spherical triangle… ### Relationships In A Spherical Triangle

Illustration used, with the law of cosines, to find the relation between the three sides and an angle… ### Relationships In A Spherical Triangle

Illustration used to extend the law of cosines when finding the relation between the three sides and… ### Relationships In A Spherical Triangle

Illustration used to extend the law of cosines when finding the relation between the three sides and… ### Right Spherical Triangle

Illustration of a right spherical triangle with a and b the sides, and α and β the angles… ### Square

Square with angles labeled. A rectangle with four equal sides. ### Two Squares With Sides of Lengths 3,4,5 Placed at Right Angles to Each Other

Two set squares, whose sides are 3,4, and 5 in., are placed so that their 4-in. sides and right angles… ### Survey of Lake Front in Chicago

Illustration showing a survey on the lake front in Chicago with distances and angle measures shown. ### Angle Ornament Symbol

The angle ornament symbol is a symbol of art. ### Theodolite

"An instrument for the measurement of horizontal angles, consisting essentially of a telescope mounted… ### Theodolite

"An instrument much employed in land-surveying for the measurement of angles horizontal and verticle."… ### Trapezoid

Trapezoid with angles and height labeled. ### 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 ### Construction of Triangle Given Angles and Base

Illustration used to construct a triangle given the length of the base and the two base angles. ### Triangle ABC

Illustration showing a triangle with angles A, B, and C labeled. ### 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… ### 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… ### Centroid of Triangle

Illustration to show medians in a triangle. It is known as the centroid. ### Circumcenter of Triangle

Illustration to show perpendicular bisectors in a triangle. It is known as the circumcenter. ### Equiangular Triangle

Illustration showing an equiangular triangle (one that has all three angles that are equal). ### Exterior And Interior Angles Of A Triangle

An illustration showing a triangle with interior angles A, B, C, and exterior angles D, and A' + B'. ### Triangle with Exterior Angles Drawn

Illustration showing a triangle with exterior angles. This can be used to show the sum of the three… ### Incenter of Triangle

Illustration to show angle bisectors in a triangle. It is known as the incenter. ### Inclined Plane Triangle

Inclined plane using right triangle and proportions ### Isosceles Triangle degrees 1, 89.5, 89.5

An isosceles triangle with angles 1, 89.5, 89.5 ### Isosceles Triangle degrees 10, 85, 85

An isosceles triangle with angles 10, 85, 85 ### Isosceles Triangle degrees 100, 40, 40

An isosceles triangle with angles 100, 40, 40 ### Isosceles Triangle degrees 101, 39.5, 39.5

An isosceles triangle with angles 101, 39.5, 39.5 ### Isosceles Triangle degrees 102, 39, 39

An isosceles triangle with angles 102, 39, 39 ### Isosceles Triangle degrees 103, 38.5, 38.5

An isosceles triangle with angles 103, 38.5, 38.5 ### Isosceles Triangle degrees 104, 38, 38

An isosceles triangle with angles 104, 38, 38