sin(A+B)=sinAcosB+cosAsinB
sin(A-B)=sinAcosB-sinBcosA？
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)
2) From the above formula, the following double-angle formula can be derived.
tan2A=2tanA/[ 1-(tanA)^2]
cos2a=(cosa)^2-(sina)^2=2(cosa)^2 - 1= 1-2(sina)^2
(The cosine above is very important)
sin2A=2sinA*cosA
3) Half-angle just remember this:
Tan(A/2)=( 1-cosA)/ Sina = Sina /( 1+cosA)
(4) The power reduction formula can be derived from the cosine of double angle.
(sinA)^2=( 1-cos2A)/2
(cosA)^2=( 1+cos2A)/2
5) Using the above power reduction formula, the following commonly used simplified formulas can be derived.
1-cosA=sin^(A/2)*2
The universal formula of 1-Sina = cos (a/2) * 2 makes tan (a/2) = tsina = 2t/(1+T2) COSA = (1-T2)/(1+). 0? 6-b？ 0? 6=(a-b)(a？ 0? 5+ab+b？ 0? 5) cubes and a? 0? 6+b？ 0? 6=(a+b)(a？ 0? 5-ab+b？ 0? 5) Complete square sum formula (A+B) 2 = A 2+2AB+B 2 Complete square difference formula (a-b) 2 = A 2-2AB+B 2 Complete cube sum formula (A+B) 3 = (A+B) (A+B) (A+) 3 = (A-B). Thank you! !