Ellipse circumference's Theorem: The circumference of an ellipse is equal to the circumference (2πb) of an ellipse with the radius of the short semi-axis length plus four times the difference between the long semi-axis length (a) and the short semi-axis length (b) of an ellipse.

Elliptic area formula:

S=πab

Ellipse area theorem: the area of an ellipse is equal to π times the product of the major semi-axis length (a) and the minor semi-axis length (b) of an ellipse.

sin(A+B)=sinAcosB+cosAsinB

; Sin (A-B)= Sinakos B.

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Simbukosa

cos(A+B)=cosAcosB

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sinAsinB

; cos(A-B)=cosAcosB

+

sinAsinB

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

cot(A+B)=(cotA cotB- 1)/(cot B+cotA)

; cot(A-B)=(cotA cotB+ 1)/(cot b-cotA)

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)=n^2

2+4+6+8+ 10+ 12+ 14+…+(2n)= n(n+ 1)

1^2+2^2+3^2+4^2+5^2+6^2+7^2+8^2+…+n^2=n(n+ 1)(2n+ 1)/6

1^3+2^3+3^3+4^3+5^3+6^3+…n^3=(n(n+ 1)/2)^2

1 * 2+2 * 3+3 * 4+4 * 5+5 * 6+6 * 7+…+n(n+ 1)= n(n+ 1)(n+2)/3

sine law

a/sinA=b/sinB=c/sinC=2R

note:

In ...

rare

Represents the radius of the circumscribed circle of a triangle.

cosine theorem

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

Note: Angle B is the included angle between side A and side C..

Vieta theorem: x1+x2 =-b/a.

x 1x2=c/a

Don't mention some simple area formulas ~