A pentagon is a closed shape made by connecting five line segments end to end, and the sum of its interior angles is 540 degrees.
Rubber geometry is the popular name for the branch of mathematics called 'topology'.
Physics is the study of the most general laws of motion of matter and the basic structure of matter. As a leading branch of natural science, it looks into everything from the vast universe to tiny fundamental particles, exploring the most basic forms and laws of motion of all matter, which makes it the foundation for research in other natural sciences. This field started back in the days of Galileo and Newton and has now grown into a fundamental science with many branches. It's both an experimental science and one that values rational thinking and logical reasoning, heavily relying on math as its working language, making it one of the most precise natural sciences today.
Elimination is a method used when solving equations to turn multiple unknowns into a single unknown. The most commonly used one in middle school is the addition-subtraction elimination method.
A coefficient is the numerical factor in a term of an algebraic expression, usually showing the quantitative relationship between variables. For example, the Pearson correlation coefficient can measure how strongly variables are related.
Decimals are a special way of expressing real numbers. All fractions can be expressed as decimals, and the dot in a decimal is called the decimal point.
Special relativity is a physics theory proposed by Einstein in 1905, and its core idea is that time and space aren't absolute—they change with speed.
In math, a chord is just the line segment that connects any two points on a curve (like a circle).
Decimal division is when you know the product of two numbers and one of the factors, and you want to find the other factor. It’s the opposite of decimal multiplication. The main trick is to turn the divisor into a whole number and then do the division like you would with integers.