• A straight line can be drawn between two points
• A finite line can be extended infinitely in both directions
• A circle can be drawn with any center and any radius
• All right angles are equal to each other
• Given a line and a point not on the line, only one line can be drawn from the point parallel to the line

• Things that equal the same thing also equals one another
• If equals are added to equals, then the wholes are equal.
• If equals are subtracted from equals, then the remainders are equal.
• Things that coincide one another equal one another.

• A point is that which has no point (Euclid)
• A point has no size
• It is used to locate position in the plane
• It is named by using a capital letter

• A line is made up of an infinite number of points
• A line is assumed to be straight
• A line has infinite length and no thickness
• Two points are needed to define a line

• A plane has length and width
• A plane has no thickness
• Need a minimum of three non-collinear points to define a plane
• Non-collinear= does not lie on a line

• On the same plane

• A ray has one fixed endpoint and continues to infinity in the other direction

• A line segment has two fixed endpoints
• The order of the letters used in naming the line segment is unimportant
• The length of a line segment can be denoted in two ways

• Congruent means coinciding at all points when superimposed
• We will study congruent angles, triangles, and segments, etc.

• An angle is formed by two rays that have a common endpoint, provided that the two rays are non-collinear.
• The common endpoint is called the vertex of the angle.
• The two rays are called the sides of the angle.

• Two angles are adjacent when they are joined by another angle

• The bisector of an angle is a rau that divides the angle into two congruentn angles.

• If points A, B, and C are collinear, and B isd between A and C, then AB+BC=AC

• A square is a quadrilateral with four congruaent sides and four angles each equal to 90°'s.

• Perpendicular lines are two lines that intersect at a 90° angle.

• Skew lines are two lines that are not coplanar and never intersect.

• A right angle is an angle measuring 90°

• An acute angle is an angle that measures greater than 0°, and is less than 90°

• An obtuse angle is a angle whose measure is more than 90°, but less than 180°.

• A reflex angle is an angle that measures greater than 180°, but less than 360°.

• Two angles are complementary if they have a sum of 90°.

• Vertical angles are formed when two lines intersect. 
• They have a common vertex but no common side.

• two angles form a linear pair if they share a common vertex and a common side and their noncommon sides form a line.

• A right triangle is a triangle that has a right angle (90°).

• An acute triangle is a triangle in which all three angles are acute (or below 90°)

• An obtuse triangle is a triangle in which one angle is obtuse (measuring more than 90°)

• A scalene triangle is a triangle that has no congruent sides.

• An equilateral triangle is a triangle that has all three congruent sides.

• An isosceles triangle is a triangle in which two of its sides are congruent.

• A straight angle is an angle whose measure is 180°

• Two angles form a linear pair if they share a common ray between them and their non-common rays form a line

• A statement accepted without proof
• (always written in the form: if..........then)

• If two angles form a linear pair then they are supplementary angles

• The reverse order of a conjecture

• If two lines intersect, then the vertical angles are congruent.

• If two lines are cut by a transversal then the corresponding angles are congruent. 

• If two parallel lines are cut by a transversal then the alternate interior angles are congruent.

• If two parallel lines are cut by a transversal, then the alternate exterior angles are congruent.

• If two parallel lines are cut by a tranversal, then the consecutive interior angles are supplementary angles.

• If two parallel lines are cut by a transversal, then the consecutive exterior angles are supplementary angles.

• A polygon is a plane, closed figure that is bound by straight lines.

• A diagonal is a line that connects two non-consecutive vertices in a polygon

• A polygon is concave if at least one of its diagonals lie outside of the polygon.

• A regular polygon is a polygon in which all sides are congruent and all angles are congruent

Regular Triangle=equilateral triangle

• The sum of the interior angles of a polygon with n sides is (n-2)×180° 

• Two pairs of consecutive interior angles that are supplementary.

• The line segment joining the midpoints of the two non-parallel sides of the trapezoid.

• A kite is a quadrilateral with two pairs of congruent adjacent sides and no parallel sides.

• Two pairs of congruent adjacent sides.
• The diagonals of a kite are perpendicular.
• The longer diagonal bisects the shorter diagonal of the kite.
• The angles at the end of the shorter diagonal are congruent.

• A=l×w

• A=s²

• 1/2bh

• A=1/2(b₁+b₂)h

• A=bh

• A=1/2d₁d₂

• A=1/2d₁d₂

• Πr²

• the center of a circumcircle

• A polyhedron is a solid in which all the faces are polygons

• A prism is a solid in which two of it's faces, called the bases, are congruent and parallel and all the side faces are parallelograms (rectangles)