Across
- 2. polygon- A convex polygon is any polygon that is not concave.
- 4. Points are geometric objects that have only location. To describe their location, we use coordinates. We begin with a standard reference frame (typically the x- and y-axes). The coordinates of a point describe where it is located with respect to this reference frame. They are given in the form (x,y) where the x represents how far the point is from 0 along the x-axis, and the y represents how far it is from 0 along the y-axis. The form (x,y) is a standard convention that allows everyone to mean the same thing when they reference any point.
- 9. A circle is the set of all points in a plane that are equidistant from a given point in the plane, which is the center of the circle.
- 10. When three or more lines meet at a single point, they are said to be concurrent. In a triangle, the three medians, three perpendicular bisectors, three angle bisectors, and three altitudes are each concurrent.
- 12. (AAA) similarity- The angle-angle-angle (AAA) similarity test says that if two triangles have corresponding angles that are congruent, then the triangles are similar. Because the sum of the angles in a triangle must be 180°, we really only need to know that two pairs of corresponding angles are congruent to know the triangles are similar.
- 13. Converse means the "if" and "then" parts of a sentence are switched. For example, "If two numbers are both even, then their sum is even" is a true statement. The converse would be "If the sum of two numbers is even, then the numbers are even," which is not a true statement.
- 17. A circle's diameter is a segment that passes through the center and has its endpoints on the circle.
Down
- 1. If angle A is an acute angle in a right triangle, the cosine of A is the length of the side adjacent to angle A, divided by the length of the hypotenuse of the triangle. We often abbreviate this as cos A = (adjacent)/(hypotenuse).
- 3. section- A cross section is the face you get when you make one slice through an object.
- 4. The circumcenter of a triangle is the point where the three perpendicular bisectors meet. This point is the same distance from each of the three vertices of the triangles.
- 5. triangle- An equilateral triangle is a triangle with three equal sides.
- 6. Two figures are congruent if all corresponding lengths are the same, and if all corresponding angles have the same measure. Colloquially, we say they "are the same size and shape," though they may have different orientation. (One might be rotated or flipped compared to the other.
- 7. An altitude of a triangle is a line segment connecting a vertex to the line containing the opposite side and perpendicular to that side.
- 8. triangle- An acute triangle is a triangle with all three angles less than 90°.
- 10. triangles- Congruent triangles are triangles that have the same size and shape. In particular, corresponding angles have the same measure, and corresponding sides have the same length.
- 11. bisector- An angle bisector is a ray that cuts the angle exactly in half, making two equal angles.
- 13. The centroid of a triangle is the point where the three medians meet. This point is the center of mass for the triangle. If you cut a triangle out of a piece of paper and put your pencil point at the centroid, you could balance the triangle.
- 14. polygon- A concave polygon is any polygon with an angle measuring more than 180°. Concave polygons look like they are collapsed or have one or more angles dented in.
- 15. angle- A central angle is an angle with its vertex at the center of a circle.
- 16. An edge is a line segment where two faces intersect.