"θ" means angle, and sinθ means sine value of θ angle. Simply put, put θ in a right triangle, and sinθ represents the ratio of the value of the right side to the value of the hypotenuse. (If θ = 90, sinθ= 1)

For example, right-angled triangular twisted strings 3, 4 and 5, assuming that the included angle between sides 4 and 5 is θ, then sinθ=3/5.

Extended data:

Sine law is a basic theorem in trigonometry, which points out that "in any plane triangle, the ratio of sine value of each side to its diagonal is equal and equal to the diameter of the circumscribed circle", that is, a/sinA = b/sinB =c/sinC = 2r=D(r is the radius of the circumscribed circle and D is the diameter).

Cosine (cosine function), a kind of trigonometric function. In Rt△ABC (right triangle), ∠ c = 90 (as shown in the figure), and the cosine of ∠A is the hypotenuse of the adjacent side of the triangle, that is, cosA=b/c, which can also be written as cosa=AC/AB. Cosine function: f(x)=cosx(x∈R).