Calculus is a branch of advanced mathematics that studies the differentiation and integration of functions and their applications. The core is to use mathematical methods to analyze rates of change and accumulated quantities. It's based on the theory of limits and consists of two main parts: differential calculus and integral calculus.

(1) Problems involving finding speed and distance during movement, (2) Problems about finding the tangent of a curve, (3) Problems about finding length, area, volume, and center of mass, (4) Problems about finding maximum and minimum values (quadratic functions, a type of calculus).

Numbers are an abstract concept used for counting, labeling, or measuring, and are a simple symbolic way to record comparisons of things of the same kind.

Volume is the amount of space an object takes up, used to measure how much room it occupies in three-dimensional space.

In math (linear algebra and geometric transformations), a horizontal shear is a type of linear transformation that keeps the area of a shape the same but slants it horizontally. The main feature is that each point’s y-coordinate stays the same, while the x-coordinate shifts proportionally based on the y value.

There are 24 hours in a day and 365 days in a year.

A private key isn't just a random number mathematically; it's a specific integer or vector generated based on a one-way trapdoor function. The core math property is computational irreversibility: it's easy to derive the public key from the private key, but you can't reverse it to get the private key from the public key in polynomial time.

Astronomy mainly studies celestial bodies in outer space, the structure and development of the universe, including the positions, structures, properties, and movement patterns of these bodies.

A quadrilateral is a closed flat shape formed by connecting four line segments end to end, and it's one of the most basic geometric shapes in math.

Quadrilaterals are mainly divided based on the parallel relationships of their sides into parallelograms, trapezoids, and general quadrilaterals, with parallelograms including rectangles, rhombuses, and squares.