Flash basic Theory Class chapter III Application of Trigonometry Ⅰ

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Starting with this chapter, we will learn trigonometry and apply it to the animation technology in the fifth chapter, actually in the next chapter of the drawing technology will be contacted. If you already have a knowledge of trigonometry or are eager to learn about animation, you can skip the start section and then come back to learn when you don't know what to do later on. The 90% trigonometry we use requires both Math.sin and Math.Cos functions. When I wrote the first edition of my book, I said that apart from the algebra and geometry that I had studied in high school (and because most of the time was too long to remember), I have not received formal training in mathematics, originally in this chapter from a variety of books, websites or other network resources, because this part of the knowledge is not difficult, Since I can learn, then you must also be able to. Now that I have completed my college algebra and calculus courses, I have a more comprehensive and systematic understanding of trigonometry. I can be honored to say that this chapter is very good because there is a deeper understanding of the subject, so many places can be explained more clearly.

What is trigonometry (trigonometry)

Trigonometry is a discipline which studies the relationship between triangles and their edges and angles. When we look at a triangle, we find that it has three edges and three corners (so called triangles), and there are some special relationships between these edges and angles. For example, if you increase any of these corners, the corresponding edges of the corners will grow (assuming that the other two edges are unchanged), and the other two corners will be smaller, in fact, how much they have changed and calculated to make a percentage. In a triangle, if one of the angles is 90 degrees, it is called a right triangle, and a square (pedal) is marked at the angle of the corner, only in a right triangle. Learning the relationship in the right triangle is much simpler than deriving the basic formula, which makes the right triangle a very useful structure, and most of the content behind this chapter and the book is a right-angled triangle.

Cape (Angle)

The angle is the main research object of trigonometry, let us solve this problem first. The angle is a graph composed of two intersecting lines, or the space between two intersecting lines, the larger the space, the greater the angle. In fact, two lines intersect to form Four corners, as shown in Figure 3-1:

Figure 3-1 Two lines form Four Corners

Radian (radian) and angle system (degress)

Radian system and angle system are two kinds of special systems in the angle measurement. We are probably the most familiar with the angle system, or even close our eyes can draw a 45-degree or 90-degree angle. The 360-degree system has become a culture, and it is often said that "a 180-degree turn" means "go in the opposite direction", not in the direction of the turn, but in the opposite view. The angle we're talking about, for a computer, is radians. So, whether you like it or not, you have to understand the radian system.

1 radians equals 57.2958 degrees. You might ask, "Is this logical?" "It does have its logic. A circle, 360 degrees, the calculated Radian is 6.2832. Still doesn't make any sense? Ok, think about Pi Pi (pi) is about equal to 3.1416, and a circle (6.2832 radians) equals 2 pi. We know that 360 degrees is equivalent to 2 pi,180 degree equivalent to pi,90 degree equivalent to PI/2, and so on. Fig. 3-2 shows some common radian systems.

Figure 3-2 Radians and angles