微分是变化率,积分则是变化率的累加。
Quadratic formula
If
a x 2 + b x + c = 0 ax^2+bx+c=0 ax2+bx+c=0
then
x = − b ± b 2 − 4 a c 2 a x=\frac{-b\pm\sqrt{b^2-4ac}}{2a} x=2a−b±b2−4ac
If
x 2 + b x + c = 0 x^2+bx+c=0 x2+bx+c=0
then
x = ( − b / 2 ) ± ( b / 2 ) 2 − a c x=(-b/2)\pm\sqrt{(b/2)^2-ac} x=(−b/2)±(b/2)2−ac
Polynomial
立方和差: a 3 ± b 3 = ( a ± b ) ( a 2 ∓ a b + b 2 ) a^3 \pm b^3 = (a\pm b)(a^2 \mp ab+b^2) a3±b3=(a±b)(a2∓ab+b2)
和差立方: ( a ± b ) 3 = a 3 ± 3 a 2 b + 3 a b 2 ± b 3 (a\pm b)^3=a^3\pm 3a^2b+3ab^2\pm b^3 (a±b)3=a3±3a2b+3ab2±b3
Trigonometric Functions
The Six Basic Trigonometric Functions
Trigonometric Identities
cos 2 θ + sin 2 θ = 1 \cos^2θ+\sin^2θ=1 cos2θ+sin2θ=1
Addition Formulas
cos ( A + B ) = cos A cos B − sin A sin B \cos(A+B)=\cos A\cos B - \sin A \sin B cos(A+B)=cosAcosB−sinAsinB
sin ( A + B ) = sin A cos B + cos A sin B \sin(A+B) = \sin A \cos B + \cos A \sin B sin(A+B)=sinAcosB+cosAsinB
Double-Angle Formulas
cos 2 θ = cos 2 θ − sin 2 θ \cos2θ = \cos^2θ - \sin^2θ cos2θ=cos2θ−sin2θ
sin 2 θ = 2 sin θ cos θ \sin2θ = 2\sinθ \cosθ sin2θ=2sinθcosθ
Half-Angle Formulas
c o s 2 θ = 1 + cos 2 θ 2 cos^2 θ = \frac{1 + \cos 2θ}{2} cos2θ=21+cos2θ
s i n 2 θ = 1 − cos 2 θ 2 sin^2 θ = \frac{1 - \cos 2θ}{2} sin