Geometric photo By: Mary byrd

Base of triangle The side of a triangle which is perpendicular to the altitude.sidetriangleperpendicularaltitude

box A box shape in three dimensional space. Formally, a polyhedron for which all faces are rectangles.three dimensional spacepolyhedronfacesrectangles

cevian A line segment, ray, or line that extends from a vertex of a triangle to the opposite side (which may be extended). Medians, altitudes, and angle bisectors are all examples of cevians.line segmentraylinevertextrianglesideMediansaltitudesangle bisectors

cosine The trig function cosine, which is written cos θ. For acute angles, cos θ can be found by theSOHCAHTOA definition, shown below on the left. The circle definition, a generalization of SOHCAHTOA, is shown below on the right. f(x) = cos x is a periodic function with period 2πtrig functionacute anglesSOHCAHTOAcircle definitionperiodic functionperiod

Circle The locus of all points that are a fixed distance from a given point.locuspointsfixed

cuboids A box shape in three dimensional space. Formally, a polyhedron for which all faces are rectangles.three dimensional spacepolyhedronfacesrectangles

cylinder A three-dimensional geometric figure with parallel congruent bases. The bases can be shaped like any closed plane figure (not necessarily a circle) and must be oriented identically.three-dimensionalgeometric figureparallelcongruentbasesplane figurecircle Note: The word cylinder often refers to a right circular cylinder.right circular cylinder

decagon A polygon with ten sidespolygonsides

Diagonal of a polygon A line segment connecting non-adjacent vertices of a polygon. Note: An n-gon has diagonals.line segmentnon-adjacentverticespolygonn-gon

dodecagon A polygon with 12 sides.polygonsides

hypotenuse The side of a right triangle opposite the right angle. Note: The hypotenuse is the longest side of a right triangle.sideright triangleright angle

Major arc The longer of the two arcs between two points on a circle.arcspointscircle

octagon A polygon with eight sides.polygonsides

rectangle A box shape on a plane. Formally, a rectangle is a quadrilateral with four congruent angles (all 90°).planequadrilateralcongruentangles

Rectangle parallelepiped A box shape in three dimensional space. Formally, a polyhedron for which all faces are rectanglesthree dimensional spacepolyhedronfacesrectangles

Square pyramid A nonnegative number that must be multiplied times itself to equal a given number. The square root of xis written or x ½. For example, since 3 2 = 9.nonnegative number Note: never refers to a negative number. Even though (–3)(– 3) = 9, we do not say that –3 is a value of. Also, if x itself is negative then is imaginary.negative numberimaginary

traoziod Trapezoid US usage, definition 1: A quadrilateral which has a pair of opposite sides which are parallel. The parallel sides are called the bases, and the other two sides are called the legs.quadrilateralsidesparallelbaseslegs US usage, definition 2: A quadrilateral which has one parallel pair of opposite sides and one non-parallel pair of opposite sides. The parallel sides are called the bases, and the other two sides are called the legs.quadrilateralparallelsidesbaseslegs UK usage: The same as the US word trapezium. The UK word trapezium means the same as the US word trapezoid, and vice-versa.trapezium Commentary: Under US definition 1, a parallelogram is a type of trapezoid. Under US definition 2, a parallelogram is not a type of trapezoid. Regardless of which definition you prefer, the trapezoid area formula can be used to find the area of a parallelogram.parallelogramtrapezoid area formula

trapezium US usage: A quadrilateral with no parallel sides.quadrilateralparallelsides UK usage: The same as the US word trapezoid. The UK word trapezoid means the same as the US word trapezium, and vice-versa.trapezoid

Truncated cone A cone or pyramid which has its apex cut off by an intersecting plane. The plane may be either obliqueor parallel to the base.conepyramidapexplaneobliqueparallelbase Note: If the truncating plane is parallel to the base the figure is called a frustumfigurefrustum

Truncated cylinder A cylinder or prism which has one base cut off by an intersecting plane. The other base is unaffected by the truncation. The truncating plane may be either oblique or parallel to the basescylinderprismbaseplaneobliqueparallel