# maths

##### Across
1. 1. The letters of ancient Greece, which are frequently used in math and science and denoted by Ψ ψ.
2. 6. For a triangle, this is the point at which the three medians intersect.
3. 8. The number 10 to the power 100,this number can be written as a 1 followed by 100 zeros.
4. 10. A sphere-like surface for which all cross-sections are ellipses.
5. 13. A curve shaped like a spring, it can be made by coiling a wire around the outside of a right circular cylinder.
6. 16. The four sections into which the x-y plane is divided by the x- and y-axes.
7. 18. A helping theorem.It is proven true, just like a theorem, but is not interesting or important enough to be a theorem. It is of interest only because it is a stepping stone towards the proof of a theorem.
8. 21. Similar geometric figures that share a common center.
9. 22. A part of a line starting at a particular point and extending infinitely in one direction.
10. 23. A statement accepted as true without proof, it should be so simple and direct that it seems to be unquestionably true.
11. 24. Set The set with no elements. The empty set can be written or {} and also known as empty set.
12. 26. Measurement of geometric figures and includes length, angle measure, area, volume.
13. 27. Quadrilateral with two pairs of adjacent sides that are congruent,also it's diagonals are perpendicular.
14. 28. A polygon with eleven sides.
15. 29. A family of related curves usually expressed in polar coordinates. The cardioid is a special kind in it.
16. 31. a doughnut shape. It is a surface of revolution obtained by revolving (in three dimensional space) a circle about a line which does not intersect the circle.
##### Down
1. 2. A three dimensional solid consisting of all points equidistant from a given point. This point is the center of the geometrical figure and all cross-sections are circles.
2. 3. A polynomial with two terms which are not like terms.eg 2x – 3, 3x5 +8x4, and 2ab – 6a2b5.
3. 4. A special case of a more general theorem which is worth noting separately. For example, the Pythagorean theorem is a ______ of the law of cosines.
4. 5. A mathematical sentence built from expressions using one or more equal signs (=).
5. 7. A parallelogram with four congruent sides and the diagonals are perpendicular.
6. 9. Any polyhedron with six faces, all of which are quadrilaterals,a regular geometric figure is a cube.
7. 11. The letters of ancient Greece, which are frequently used in math and science and denoted by Σ σ.
8. 12. A transformation that is invariant with respect to distance. That is, the distance between any two points in the pre-image must be the same as the distance between the images of the two points.
9. 14. A polyhedron with six faces, all of which are parallelograms.
10. 15. The eight regions into which three dimensional space is divided by the x-, y-, and z-axes.
11. 17. The property of real numbers which guarantees that for any two real numbers a and b, exactly one of the following must be true: a < b, a = b, or a > b.
12. 19. A line segment, line, or plane that divides a geometric figure into two congruent halves.
13. 20. A polygon with ten sides.
14. 25. A number which is a multiply by five.
15. 30. A rectangular (or square) array of numbers, it can be written using brackets or parentheses.