LinesPlane – A flat surface that has no thickness and extends forever.

Point – an exact location

Line – a straight path that has no thickness and extends forever in opposite directions

Ray – Part of a line that has one endpoint and extends forever in one direction.

Line Segment – Part of a line that has two endpoints.

Congruent – figures that have the same shape or size. (Same length for line segments).

Perpendicular lines – Two lines that make a 90 angle when they intersect.

Parallel Lines – Lines that never intersect.

ANGLES

Right Angle – an angle that measures exactly 90o.

Acute Angle – An angle that measures greater than 0 o but less than 90 degrees.

Obtuse Angle – An angle that measures greater than 90 o but less than 180 o.

Straight Angle – Angle that measures exactly 1800.

Complementary angles – The sum of two angles equals 900.

Supplementary Angles – The sum of two angles equals 1800.

Adjacent angles – have a common vertex and a common side.

Vertical angles – opposite angles formed by two intersecting lines.

Transversal – a line that intersects two or more lines.

Properties of Transversals to Parallel Lines1. Corresponding angles are congruent2. Alternate interior angles are congruent

Polygons

Polygon – a closed plane figure formed by three or more line segments.

Regular Polygon – a polygon in which all sides and all angles are congruent.

Triangle – 3 sides, 3 angles Quadrilateral – 4 sides, 4 angles

Pentagon – 5 sides, 5 angles Hexagon – 6 sides, 6 angles

Heptagon – 7 sides, 7 angles Octagon – 8 sides, 8 angles

Nonagon – 9 sides, 9 angles Decagon – 10 sides, 10 angles

TrianglesScalene triangle – no congruent sides.

Isosceles triangle – at least two congruent sides.

Equilateral triangle – all sides are congruent.

Acute triangle – all angles are acute

Obtuse triangle – has exactly one obtuse angle

Right Triangles

Right Triangle – has exactly one right angle.

Legs – two sides the form the right angle in a right triangle

Hypotenuse – The side opposite the right angle in a right triangle. It is also the longest side.

The Pythagorean Theorem – A special relationship between the sides of a right triangle.

a2+b2=c2

Areas of Polygons

Area of a Triangle -

A=12 bh

Area of a Rectangle -

A=lw

Area of a Parallelogram -

A=bh

QuadrilateralsParallelogram – Opposite sides and opposite angles are congruent.

Rectangle – Parallelogram with four right angles

Rhombus – Parallelogram with four congruent sides.

Square – Parallelogram with four congruent sides and angles.

Trapezoid – A quadrilateral where exactly one pair of opposite sides are parallel.

Polygon MeasurementsThe sum of the measures of a triangle is 180.

The sum of the measures of a quadrilateral is 360.

Perimeter the distance around a geometric figure. To find the perimeter, add the lengths of it’s sides.

Perimeter of a rectangle:

P=2 l+2w

There are 3600 degrees in a circle.

Area of a Circle: A=πr 2

C=πdC=2πr

Circumference of a circle.

an arc connecting them.enclosed by the two radii and Sector – part of the circle

Central Angle – An angle formed by two radii (radius).

Arc – Part of a circle named by it’s endpoints.

Chord – Line segment whose endpoints are any two points on a circle.

Radius – Line segment whose endpoints are the center of a circle and any point on the circle.

Diameter – Line segment that passes through the center of a circle and whose endpoints lie on the circle.

Circle – all points in a plane that are the same distance from a given point, called the center of a circle.

Circles