sin(A+B)= Sina cosb+cosa sinb sin(A-B)= Sina cosb-sinb cosa

cos(A+B)= cosa cosb-Sina sinb cos(A-B)= cosa cosb+Sina sinb

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

Ctg (a+b) = (ctgactgb-1)/(ctgb+ctga) ctg (a-b) = (ctgactgb+1)/(ctgb-ctga) multiple angle formula.

tan2A = 2 tana/( 1-tan2A)ctg2A =(ctg2A- 1)/2c TGA

Cos2a = cos2a-sin2a = 2cos2a-1=1-2sin2a half-angle formula

sin(A/2)=√(( 1-cosA)/2)sin(A/2)=-√(( 1-cosA)/2)

cos(A/2)=√(( 1+cosA)/2)cos(A/2)=-√(( 1+cosA)/2)

tan(A/2)=√(( 1-cosA)/(( 1+cosA))tan(A/2)=-√(( 1-cosA)/(( 1+cosA))

CTG(A/2)=√(( 1+COSA)/(( 1-COSA))CTG(A/2)=-√(( 1+COSA)/(( 1-COSA))。

2 Sina cosb = sin(A+B)+sin(A-B)2 cosa sinb = sin(A+B)-sin(A-B)

2 cosa cosb = cos(A+B)-sin(A-B)-2 sinasinb = cos(A+B)-cos(A-B)

sinA+sinB = 2 sin((A+B)/2)cos((A-B)/2 cosA+cosB = 2 cos((A+B)/2)sin((A-B)/2)

tanA+tanB = sin(A+B)/cosa cosb tanA-tanB = sin(A-B)/cosa cosb

The sum of the first n terms in some sequences of ctga+ctgbsin (a+b)/sinasib-ctga+ctgbsin (a+b)/sinasib.

1+2+3+4+5+6+7+8+9+…+n = n(n+ 1)/2 1+3+5+7+9+ 1 1+ 13+ 15+…+(2n- 1)= N2

2+4+6+8+ 10+ 12+ 14+…+(2n)= n(n+ 1) 12+22+32+42+52+62+72+82+…+N2 = n(n+ 1)(2n+ 1)/6

13+23+33+43+53+63+… n3 = N2 (n+1) 2/41* 2+2 * 3+3 * 4+4 * 5 * 6 *. Cosine Theorem b2=a2+c2-2accosB Note: Angle B is the included angle between side A and side C, and the arc length formula L =>-B ≤ A ≤ B | A-B |≥| |-A |≤ A | Solution of a quadratic equation with one variable-B+√ (B2-4ac)/2a-.

B2-4ac=0 Note: This equation has two equal real roots.

B2-4ac >0 Note: The equation has two unequal real roots.

B2-4ac & lt； Note: The equation has no real root, but a complex number of the yoke.

Reduced power formula

(sin^2)x= 1-cos2x/2

(cos^2)x=i=cos2x/2

General formula of trigonometric function

Let tan(a/2)=t

sina=2t/( 1+t^2)

cosa=( 1-t^2)/( 1+t^2)

tana=2t/( 1-t^2)

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