How to find sine and cosine values

Sine value: opposite side/hypotenuse of sine = ∠ a.

Cosine value: cosA=b/c, which can also be written as cosa=AC/AB. Cosine function: f(x)=cosx(x∈R).

Sine theorem: for triangles with side lengths a, b and c and corresponding angles a, b and c, there are: Sina/a = sinb/b = sinc/c; It can also be expressed as: a/sina = b/sinb = c/sinc = 2r; Deformation: A = 2RSINA, B = 2RSINB, C = 2RSINC where R is the radius of the circumscribed circle of the triangle.

Cosine theorem: for triangles with side lengths a, b and c and corresponding angles a, b and c, there are: a? = b？ + c？ -cosAb in 2000 BC? = a？ + c？ -2ac cosB； c？ = a？ + b？ -2ab cosC； It can also be expressed as:

cosC=(a？ +b？ -c？ )/2ab； cosB=(a？ +c？ -B? )/2ac； cosA=(c？ +b？ -a？ )/2 BC.

Extended data:

Sum of squares relation

(sinα)^2 +(cosα)^2= 1

Product relationship

Sinα = tanα × cosα (that is, sinα/cosα = tanα)

Cosα = cotα × sinα (that is, cosα/sinα = cotα).

Tanα = sinα × secα (that is, tanα/sinα = secα).

Reciprocal relationship

tanα × cotα = 1

sinα × cscα = 1

cosα × secα = 1