Let three sides of a triangle be a b c, their diagonal corners be A B C, and the radius of the circumscribed circle be R, then the relation a/sinA=b/sinB=c/sinC is a sine theorem.

Cosine theorem:

Let three sides of a triangle be B C and their diagonal corners be b c, then this relationship is called:

a^2=b^2+c^2-2bc*cosA

b^2=c^2+a^2-2ac*cosB

c^2=a^2+b^2-2ab*cosC

The trigonometric function sin cos tan corresponds as follows:

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.