Tan α cotα =1sin α CSC α =1cos α secα =1quotient relation: sin α/cos α = tan α = sec α/CSC α cos α/sin α = cot α = CSC α/secα square relation: SIN 2 (α

Two commonly used formulas under different conditions

Sin 2 (α)+cos 2 (α) =1tan α *cot α= 1

Special formula

(sina+sinθ) * (sina-sinθ) = sin (a+θ) * sin (a-θ) Proof: (sina+sinθ) * (sina-sinθ) = 2sin [(θ+a)/2] cos [(a-θ)/2].

slope formula

We usually refer to the ratio of the vertical height h to the horizontal height l of the half slope as slope (also called slope ratio), which is expressed by the letter I, that is, I = h/L. The general form of slope is written as l: m, such as i= 1:5. If the angle between the slope and the horizontal plane is recorded as a (called the slope angle), then I = h/l = tan a.

Acute angle formula of trigonometric function

Sine: the hypotenuse cosine of the opposite side of sin α = ∠ α/α: the hypotenuse tangent of the adjacent side of cos α = ∠ α/α: the cotangent of the opposite side of tan α = ∠ α/α = ∠α.

Double angle formula

Sin2A=2sinA cosA cosine 1. Cos2a = Cos2 (a)-Sin2 (a) 2。 Cos2a = 1-2sin 2 (a) 3。 Cos2a = 2cos 2 (a)- 1, that is. -1 = 1-2 sin 2 (a) tangent tan2a = (2 tana)/( 1-tan 2 (a))

The universal formula sin α = 2tan (α/2)/[1+tan2 (α/2)] cos α = [1-tan2 (α/2)]/[1+tan2 (α/2)] tan.