definition of terms in geometry

1. Tansversal – a line thatintersecttwodifferentlinesattwodifferentpoints.
ExteriorAngles –angles1, 2, 7, and 8 are exteriorangles
InteriorAngles –angles3, 4, 5, and 6 are interiorangles
CorrespondingAngles–a pairof exteriorandinterioranglesonthe same side of transversal thatdonot
forma linearpair.Angles1& 5, 2 & 6, 4&8, and 3&7
Alternate InteriorAngles –a pairof interioranglesonoppositesidesof atransversal thatdo not forma
linearpair.Angles4&6, and 3 & 5.
Alternate ExteriorAngles –a pairof exterioranglesonopposite sidesof transversal thatdonotforma
linearpair.
Polygon– a closedfigure whose sidesare segments. Sidesof apolygondoncrosseachother norlie on
the same line.
No. of sides Name
3 Triangle
4 Quadrilateral
5 Pentagon
6 Hexagon
7 Heptagon
8 Octagon
9 Nonagon
10 Decagon
11 Undecagon
12 Dodecagon
n n-gon
RegularPolygon –is a convex polygonall of itssidesandanglescongruent.
Non-regularPolygon –iseitherconvex ornon-convex polygonwhose sidesoranglesare notof the same
measure.
1
3
2
4
5 6
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2. Convex Polygon –a polygonisconvex if the segmentjoininganytwopointscontainingitlie entirelyin
the interiorof the polygon.
Non-convex Polygon –a polygonisnon-convex if the segmentjoininganytwopointscontainingitdo
not lie entirelyinthe interiorof the polygon.
Triangle – any polygonwiththree sidesor3 angles.
Classificationof TrianglesaccordingtoAngles
a. Acute Triangles – are trianglesall of itsanglesare acute
b. RightTriangles – are triangleswithone rightangle
c. Obtuse Triangles –are triangleswithone obtuse angle.
Classificationof Trianglesaccordingtothe Numberof CongruentSides
a. Scalene Triangles –are triangleswhereinnotwoof its sidesare of equal measure
b. IsoscelesTriangles –are triangleswithtwoof itssidescongruent.
c. Equilateral Triangles–are trianglesall of itssidesare congruent.
Quadrilaterals– are polygonswithfoursidesorfourangles.
Parallelogram–a quadrilateral withtwopairsof opposite side parallel.
Rectangle – a parallelogramall of itsanglesare rightangles.
Rhombus – a parallelogramall of itssidesare congruent.
Square – isa rectangle all of itssidesare congruent
Trapezoid– isa quadrilateral withone pairof opposite sidesparallel.
Kite – is a quadrilateral withtwopairsof consecutivesidescongruent.
Circle – isa set of pointsequidistantfromafixedpointcalledcenter.
Radius– a segmentjoiningapointonthe circle and itscenter.
Diameter– isa chord that containsthe centerof the circle.
Chord– isa segmentwhose endpointsare pointsonthe circle.
Arc – part of a circle whose endpointsare the endpointsof the chordthat subtendsit.
Semi-Circle–an arc whose endpointsare the endpointsof the diameterof the circle.
Sector– isthe regionboundedbythe sidesof acentral angle andthe arc subtendedbythe angle.
Tangentof a circle – is a line thatintersectacircle at exactlyone pointcalledpointof tangency.

3. Secantof a circle – isa line thatintersecta circle at twodifferentpoints.
Major Arc – an arc whose measure isgreaterthanthe measure of a semi-circle.
Minor Arc – an arc whose measure islessthanthe measure of a semi-circle