Sin= = The opposite side is greater than the hypotenuse.

Cosine cos= the ratio of adjacent side to hypotenuse.

Tangent tan= the opposite side is closer to the adjacent side.

1, sine, mathematical term. In a right triangle, the ratio of the opposite side to the hypotenuse of any acute angle ∠A is called the sine of ∠A, which is abbreviated from the English word sine, that is, the opposite side/hypotenuse of Sina = ∠ A.

2. Cosine (cosine function), a kind of trigonometric function. In Rt△ABC (right triangle), ∠ C = 90, and ∠A's cosine is the hypotenuse of its adjacent side than the triangle, that is, cosA=b/c, which can also be written as cosa=AC/AB.

3. In RT △ ABC (right triangle), ∠C = 90, AB is the opposite side C of ∠ C, BC is the opposite side A of ∠A, AC is the opposite side B of ∠B, and the tangent function is tanB=b/a, that is, tanB=AC/BC.

Other information of cos formula:

It is a periodic function with a minimum positive period of 2π. When the independent variable is 2kπ(k is an integer), the maximum value of the function is1; When the independent variable is (2k+ 1)π, the function has a minimum value of-1, and the cosine function is an even function, and its image is symmetrical about y axis.

Using cosine theorem, we can solve the following two kinds of problems about triangles:

(1) Given three sides, find three angles.

(2) Knowing the angles between two sides and them, find the third side and the other two angles.