| Week | Topic and action |
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| Week 16 | |
Number Sequence (2)
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Planes, Points and Lines
- A plane is a flat surface that keeps going on forever in all directions as shown below.
- A tiny dot in a plane is called a point.
- A line segment is the section of line connecting two points as shown below.
- A point usually is named with a letter (such as point A and B in the above diagram), and a line segment is usually named by two letters with a bar over them (such as AB).
- The difference between a line and a line segment is that a line segment has beginning and ending points, while a line goes on forever in both directions with no endpoints. A line can be named with any two points along the line ( Such as CD (or CD↔) in the diagram below).
- A ray is a one direction of a line. It has one endpoint and continues forever in the other direction. A ray can be named with its end point and another point along the ray. Below EF→ is a ray.
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Angles
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- A right angle equals 90°. An acute angle is less than 90° and an obtuse angle is larger than 90°.
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Polygons
- A polygon is a closed plane figure with three or more sides (or angles). The smallest number of sides (or angles) a polygon could have is three and such a polygon is called a triangle.
- The points where the sides of a polygon meet are called vertices. The number of vertices of a polygon equals to the number of sides or the number of angles. The below triangle ABC has three vertices A, B, and C. It has three sides AB, BC, and CA. It also has three angles ∠A, ∠B, and ∠C.
- If each of the three angles of a triangle is less than 90°, it is an acute triangle (such as ΔABC above).
- If one of the angles equals to 90°, it is a right triangle (such as ΔDEF above).
- If one of the angles larger than 90°, it is an obtuse triangle (such as ΔOPQ above).
- If two sides are equal in a triangle, it is called an isosceles triangle.
- If all sides are equal in a triangle, it is called an equilateral triangle. An equilateral triangle is an isosceles triangle.
- A polygon with four sides is called quadrilateral.
- A parallelogram is a quadrilateral with two pairs of parallel sides. Square, rectangle, rhombus are parallelogram.
- A rectangle is a quadrilateral with all four angles being right angles. A rectangle is a parallelogram.
- A rhombus is a quadrilateral with all four sides of equal length. A rhombus is also a parallelogram.
- A square is a quadrilateral with all four sides of equal length and all four angles being right angles. A square is also a parallelogram, a rectangle, and a rhombus.
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Circles and Ellipses
- In geometry, an ellipse is a plane curve that results from the intersection of a cone by a plane in a way that produces a closed curve.
- A circle is a special case kind of ellipse, is a plane curve that results from the intersection of a cone by a plane in a way that produces a closed curve.
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Congruent and Similar
- Congruent figures are the same size and shape. The following pairs of figures are congruent.
- Similar figures are the same shape.
The following pairs of figures are similar.
- Note that all circles are similar. All squares are similar. All regular polygons with the same number of sides are similar.