2.  Conjecture- unproven statement that is based on observations.  Inductive reasoning- looking for patterns and making conjectures is part of this process  Counterexample- example shows a conjecture is false.

3.  Point- no dimensions.  Line- extends in one dimension.  Plane- extends in two directions.  Collinear points- points that lie on the same line.  Coplanar points- points that lie on the same plane.

4.  Acute angles- less than 90 degrees  Right angles- equal to 90 degrees  Obtuse angles- more than 90 degrees  Straight angles- equal to 180 degrees  Complementary angles- sum of measures is 90 degrees.  Supplementary angles- sum of measures is 180 degrees.

5.  Distance Formula- › AB=Square root of(x-x1)²+(y2-y1)²  Pythagorean Theorem-  a²+b²=c²

7.  Parallel lines- coplanar and do not intersect.  Transversal- a line that intersects two or more coplanar lines at different points.  Corresponding angles- if they occupy corresponding positions.  Alternate exterior angles- if they lie outside the two lines on opposite sides of the transversal.  Alternate interior angles- if they lie between the two lines on opposite sides of the transversal.  Consecutive interior angles- if they lie between the two lines on the same side of the transversal.

8.  Theorem 3.1 › If two lines intersect to form a linear pair of congruent angles, then the lines are perpendicular.  Theorem 3.2 › If two sides of two adjacent acute angles are perpendicular, then the angles are complementary.  Theorem 3.3 › If two lines are perpendicular, then they intersect to form four right angles.

9.  Theorem 3.4- Alternate Interior Angles › If two parallel lines are cut by a transversal, then the pairs of alternate interior angles are congruent.  Theorem 3.5- Consecutive Interior Angles › If two parallel lines are cut by a transversal, then the pairs of consecutive interior angles are supplementary.  Theorem 3.6- Alternate Exterior Angles › If two parallel lines are cut by a transversal, then the pairs of alternate exterior angles are congruent.

11.  Vertex - each of the three points joining the sides of a triangle.  Adjacent sides- two sides sharing a common vertex.  Hypotenuse- side opposite of the right angle.  Congruent- correspondence between their angles and sides.

12.  Names of Triangles › Equilateral › Isosceles › Scalene  Classification by angles › Acute › Equiangular › Right › Obtuse

13.  Reflexive Property › Every triangle is congruent to itself.  Symmetric Property › If triangle ABC is congruent to triangle DEF, the triangle DEF is congruent to triangle ABC.  Transitive Property › If triangle ABC is congruent to triangle DEF and triangle DEF is congruent to triangle JKL, then triangle ABC is congruent to triangle JKL.

14.  Side- Side-Side  Side-Angle-Side  Angle-Side-Angle  Angle-Angle-Side

16.  Convex- if no line that contains a side of the polygon contains a point in the interior of the polygon.  Concave- a polygon that is not convex.  Diagonal- a segment that joins two nonconsecutive vertices.

17.  Theorem 6.6 › If both pairs of opposite sides of a quadrilateral are congruent, then the quadrilateral is a parallelogram.  Theorem 6.7 › If both pairs of opposite angles of a quadrilateral are congruent, then the quadrilateral is a parallelogram.  Theorem 6.8 › If an angle of a quadrilateral is supplementary to both of its consecutive angles, then the quadrilateral is a parallelogram.

18.  Preimage- original figure.  Image- new figure  Transformation- operation that moves the preimage to the image.  Translation- a transformation that maps every two points.

19.  Theorem 7.2 Rotation Theorem › A rotation is an isometry.  Theorem 7.3 › If lines k and m intersect at point P, then a reflection in k followed by a reflection in m is a rotation about point P.

20.  Proportion- an equation that equates two ratios.  Geometric mean- two positive numbers a and b is the positive number x such that a/x=x/b.  Similar polygons- when there is a correspondence between two polygons such that their corresponding angles are congruent and the lengths of corresponding sides are proportional.

21.  Side-Side-Side › If the lengths of the corresponding sides of two triangles are proportional, then the triangles are similar.  Side-Angle-Side › If an angle of one triangle is congruent to an angle of a second triangle and the lengths of the sides including these angles are proportional, then the triangles are similar.

22.  Special right triangles- have measures of 45-45-90 or 30-60-90.  Sin, cosine, tangent- three basic trigonometric ratios.  Trigonometric ratio- ratio of the lengths of two sides of a right triangle.

23.  Theorem 9.8 45-45-90 Triangle › In a 45-45-90 triangle, the hypotenuse is square root of 2 times as long as each leg.  Theorem 9.9 30-60-90 Triangle › In a 30-60-90 triangle, the hypotenuse is twice as long as the shorter leg, and the longer leg is square root of 3 times as long as the shorter leg.

25.  Diameter- distance across the circle.  Radius- distance from center to point on the circle.  Chord- segment whose endpoints are points on the circle.  Secant- a line that intersects a circle in two points.  Tangent- a line in the plane of a circle that intersects the circle in exactly one point.

26.  Minor arc- part of a circle that measures less than 180 degrees.  Major arc- part of a circle that measures between 180 degrees and 360 degrees.  Semicircle- if the endpoints of an arc are the endpoints of diameter, then it is a semicircle.

27.  Theorem 10.1 › If a line is tangent to a circle, then it is perpendicular to the radius drawn to the point of tangency.  Theorem 10.2 › In a plane, if a line is perpendicular to a radius if a circle at its endpoint on the circle, then the line is tangent to the circle.

29.  Circumference- is the distance around the circle.  Arc length- portion of the circumference of a circle.  Semicircle- one half of the circumference.  To find the sum of the measures of interior angles of a polygon- › 180 multiplied by the number of sides.

30.  Given that the radius of the circle is 5 cm, calculate the area of the shaded sector. (Take π = 3.142). Area of Sector= =13.09cm²

31.  Finding Arc Length Or you can use this step:

32.  Theorem 11.4 – Area of Regular Polygons › The area of a regular n-gon with side length s is half the product of the apothem a and the perimeter P, so A=(1/2)aP or A=(1/2)aXns.  Theorem 11.8 › The ratio of the area A of a sector of a circle to the area of the circle is equal to the ratio of the measure of the intercepted arc to 360 degrees.

33.  Faces- a solid that is bounded by polygons.  Edge- line segment formed by the intersection of two faces.  Vertex- point where three or more edges meet.