1, the definition of mathematical trigonometric function
In a right triangle, for ∠ α, there are opposite side A, adjacent side B and hypotenuse C, then there are:
Sine formula: opposite side/hypotenuse of sin α = α=∞α= A/C = Y/r/r.
Cosine formula: adjacent side/hypotenuse of cosine α = α=∞α= b/c = x/r/r.
Tangent formula: tan α = ∠ α = ∠ opposite side of α/∠ adjacent side of α = a/b = y/x.
2. The key formula of mathematical trigonometric function
General formula of trigonometric function
sin=/
cos=/
tan=/
Two-angle sum and difference formula
sin=sinα cosβ+cosα sinβ，sin=sinα cosβ-cosα sinβ
cos=cosα cosβ-sinα sinβ，cos=cosα cosβ+sinα sinβ
tan=/，tan=/
Sum-difference product formula
sinA+sinB=2sincos
sinA-sinB=2cossin
cosA+cosB=2coscos
cosA-cosB =-2 sin
tanA+tanB=sin/cosAcosB=tan
tanA-tanB=sin/cosAcosB=tan
3. Mathematical trigonometric function value of special angle
1、30 =π/6
sin 30 = 1/2； Cos30 = semi-root number three; Tan30 = three-thirds root.
2、45 =π/4
Sin 45 = COS 45 = root number two, Tan 45 = 1.
3、60 =π/3
Sin60 = semi-root number three, COS60 = 1/2, tan60 = root number three.
4、90 =π/2
sin90 = 1，coa90 =0
4. Mathematical trigonometric function relation formula
1, reciprocal relation: tanαcotα= 1, sinαcscα= 1, cosαsecα= 1.
2. Quotient relation: tan α = sin α/cos α, cot α = cos α/sin α.
3. Square relation: _+_= 1