英语流利说 Level 4 Unit1 Part2 Vocabu

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

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

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

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

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

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

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.

A sphere is a three dimensional figure with a radius and a volume, which is four thirds PI R cubed.

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

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

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