The ratio of the opposite side to the hypotenuse of ∠ α (not a right angle) in a right triangle is called the sine of ∠α, and it is called the opposite side/hypotenuse of sinα=∠α. Sinα is written as sinus in Latin.

Sine is the ratio of the opposite side to the hypotenuse of ∠ α (non-right angle), and cosine is the ratio of the adjacent side to the hypotenuse of ∠α (non-right angle).

Put the Pythagorean line in the circle. A chord is a line connecting two points on a circle. The largest chord is the diameter. If the chord of a right triangle is placed on the diameter, the chord is a long chord, that is, sine, and the hook is a short chord, that is, cosine.

Extended data:

Sine function theorem: in a triangle, the ratio of sine of each side to its diagonal is equal, that is, a/sin A = b/sin B = c/sin C.

Application of sine function theorem in calculating triangle area

S△=c？ SinAsinB/2sin(A+B)(S△ is the area of triangle, with three angles ∠A∠B∠C and opposite sides ∠ A, B and C respectively).

Sdelta =1/2acsinb =1/2bcsina =1/2absinc (three angles ∠A∠B∠C, opposite sides are A, B and C respectively, see trigonometric function).

In addition, when the value of sin is between 180~360, a negative value will appear, and it will appear repeatedly above 360.

Trigonometric functions have important applications in complex numbers. Trigonometric function is also a common tool in physics.

In RT△ABC, if the acute angle A is determined, then the ratio of the opposite side to the adjacent side of the angle A is determined accordingly. This ratio is called the tangent of angle α, and is written as tanA.

That is, tanA= the opposite side of angle a/the adjacent side of angle a.

Similarly, in RT△ABC, if the acute angle A is determined, the ratio of the opposite side to the hypotenuse of the angle A is determined accordingly. This ratio is called sine of angle α, and is recorded as sinA.

That is, sinA= the opposite side of angle a/the hypotenuse of angle a.

Similarly, in RT△ABC, if the acute angle A is determined, the ratio of the adjacent side to the hypotenuse of the angle A is determined accordingly. This ratio is called cosine of angle α, and is recorded as cosA.

That is, cosA= the adjacent side of angle A/the hypotenuse of angle A. ..

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