sin(π+α)=-sinα.cos(π+α)=-cosα.tan(π+α)=tanα.

sin(-α)=-sinα.cos(-α)=cosα.tan(-α)=-tanα.

sin(π-α)=sinα.cos(π-α)=-cosα. tan(π-α)=-tanα.

sin(2π-α)=-sinα.cos(2π-α)=cosα.tan(2π-α)=-tanα.

sin(π/2+α)=cosα.cos(π/2+α)=-sinα.

sin(π/2-α)=cosα.cos(π/2-α)=sinα.

sin(3π/2+α)=-cosα. cos(3π/2+α)= sinα.

sin(3π/2-α)=-cosα. cos(3π/2-α)=-sinα.

Basic relationship: sin 2 (a)+cos 2 (a) = 1. tanA=sinA/cosA .

Trigonometric identity transformation formula: sin(A+B)=sinAcosB+cosAsinB

sin(A-B)=sinAcosB-cosAsinB

cos(A+B)=cosAcosB-sinAsinB

cos(A-B)=cosAcosB+sinAsinB

tan(A+B)=(tanA+tanB)/( 1-tanA tanB)

tan(A-B)=(tanA-tanB)/( 1+tanA tanB)

sin2A=2sinAcosA

cos2A=cos^2(A)-sin^2(A)

tan2A=(2tanA)/( 1-tan^2(A))

Sine theorem: If A, B and C are three sides of an arbitrary triangle ABC and A, B and C are three angles, then: a/sinA=b/sinB=c/sinC.

Cosine theorem: As mentioned above, then A 2 = B 2+C 2-2 BCCOSA.

b^2=a^2+c^2-2accosB

c^2=a^2+b^2-2abcosC

Generally speaking, the square of any one side is equal to the sum of the squares of the other two sides minus the product of the cosine of the other two sides and their included angles.

As for the sum-difference formula and the difference-product formula, they have been deleted from the textbook and will not be introduced again. The above is the most important content of trigonometric function to be mastered in middle school, which is played by hand and not copied. Thank you.