Such as! How to treat the positive and negative of sine quadrant in trigonometric function!

In trigonometric function, the positive and negative of sinx in each quadrant are: one quadrant is positive, two quadrants are positive, three quadrants are negative, and four quadrants are negative.

In trigonometric function, the positive and negative of cosx in each quadrant are one positive, two negative, three negative and four positive in turn; The positive and negative signs of each quadrant tanx are 1 positive 2 negative 3 positive 4 negative; The plus or minus of cotx in each quadrant is 1 plus 2 minus 3 plus 4 minus.

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.

Extended data:

1, the periodicity of the function sinX: the minimum positive period is 2π.

2. The parity of the function sinX: odd function (its image is symmetrical about the origin).

3. Monotonicity of function sinX: increasing function on [-(π/2)+2kπ, (π/2)+2kπ] and k∈Z; It is a decreasing function on [(π/2)+2kπ, (3π/2)+2kπ] and k ∈ z.