Sine is equal to the hypotenuse of the opposite side,
Cosine is equal to the ratio of adjacent side to hypotenuse.
The tangent is equal to the opposite side than the adjacent side;
Cotangent equals the comparison of adjacent edges.
Secant is equal to the hypotenuse than the adjacent edge.
Cotangent is equal to the hypotenuse compared to the edge.
Tangent and cotangent are reciprocal. 2. The relationship between complementary trigonometric functions. sin(90 -α)=cosα，cos(90 -α)=sinα，
Tan (90-α) = COT α，COT (90-α) = Tan α。 3. The square relation between trigonometric functions with the same angle:
sin^2(α)+cos^2(α)= 1
tan^2(α)+ 1=sec^2(α)
cot^2(α)+ 1=csc^2(α)
Relationship between products:
sinα=tanα cosα
cosα=cotα sinα
tanα=sinα secα
cotα=cosα cscα
secα=tanα cscα
cscα=secα cotα
Reciprocal relationship:
tanα cotα= 1
sinα cscα= 1
cosα secα= 1
In the right triangle ABC,
The sine value of angle a is equal to the ratio of the opposite side to the hypotenuse of angle a,
Cosine is equal to the adjacent side of angle a than the hypotenuse.
The tangent is equal to the opposite side of the adjacent side,
Cotangent equals adjacent edge [edit this paragraph ]4. Trigonometric function value (1) Special angle trigonometric function value.
(2) Check the trigonometric function value at any angle from 0 to 90.
(3) the change of the value of acute trigonometric function
(i) The values of acute trigonometric functions are all positive.
(ii) When the angle changes from 0 to 90 degrees,
Sine value increases (or decreases) with the increase (or decrease) of angle.
The cosine value decreases (or increases) with the increase (or decrease) of the angle.
The tangent value increases (or decreases) with the increase (or decrease) of angle.
The cotangent value decreases (or increases) with the increase (or decrease) of angle.
(iii) When the angle varies between 0 and 90,
0≤sinα≤ 1， 1≥cosα≥0，
When the angle is 0.
tanα& gt； 0，cotα& gt； 0.
"Acute trigonometric function" belongs to trigonometry and is an important content in the field of "space and graphics" of mathematics curriculum standard. According to the mathematics curriculum standard, middle school mathematics divides trigonometry into two parts, the first part is in the third stage of compulsory education, and the second part is in the high school stage. The third stage of compulsory education mainly studies the content of acute triangle function and the solution of right triangle. This textbook has a chapter called "Acute Trigonometric Function". Trigonometry in senior high school is the main part of trigonometry, including solving oblique triangles, trigonometric functions, inverse trigonometric functions and simple trigonometric equations. The former part is the important foundation of the latter part, both in content and way of thinking. Mastering the concept of acute trigonometric function and the method of solving right triangle is an important preparation for learning trigonometric function and solving oblique triangle.