懂你英语Level4-Unit1-Part2-[4]Vocabulary:Geometry

1. The two lines on the left intersect each other at a right angle, which is 90 degrees.

2. The two lines on the right are parallel, which means they never cross.

3. The adjacent sides of a rectangle are perpendicular, which means they meet at a 90 degree angle.

4. The opposite sides of a rectangle are equal and parallel, which means they never cross.

5. The area of a rectangle is the length times the width.

6. A circle is a two dimensional figure with a radius and circumference, which is the distance around the circle.

7. The area of a circle is PI R squared, where R is the radius and PI is the ratio of a circle's circumference to its diameter.

8. A sphere is a three dimensional figure with a radius and a volume, which is 4/3 PI R cubed.

9. All points on the surface of a sphere are equidistant from its center.

10. A right triangle is a two dimensional figure with 3 sides, two of which are perpendicular.

11. To find its area, multiply the length of the two perpendicular sides, A & B, and divided by two, A equals one half A B.

A rectangle is a two dimensional figure with 4 sides.（前文未见生句）

Pi is the ratio of a circle’s circumference to its diameter.（前文未见生句）