Level 4 - Unit 1 - Part 2 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.
左边两条线以直角（90度）相交。右边两条线平行，永不相交。

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.
矩形的邻边垂直，也就是说以90度角相交。矩形的对边相等且平行，永不相交。矩形的面积等于长乘以宽。

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.
圆是一种二维图形，有半径和周长，周长是环绕圆一周的长度。圆的面积是pi*r平方，r是半径，pi是圆的周长和直径的比值。

A sphere is a three dimensional figure with a radius and a volume, which is 4/3 pi r cubed. All points on the surface of a sphere are equidistant from its center.
球形是一种三维图形，有半径和体积，体积为4/3 * pi * r立方。球面上的所有点距离圆心相等。

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 and b, and divided by two. A equals one half A B.
直角三角形是一种二维图形，有三条边，其中两条互相垂直。面积等于两条垂直边a和b的长度的乘积再除以2，即A=1/2ab。