微积分公式

微分是变化率，积分则是变化率的累加。

Quadratic formula

If
$a{x}^2+bx+c=0$
then
$x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}$

If
$x^2+bx+c=0$
then
$x=(-b/2)\pm \sqrt{(b/2{)}^2-ac}$

Polynomial

立方和差: $a^3\pm b^3=(a\pm b)(a^2\mp ab+b^2)$
和差立方：$(a\pm b{)}^3=a^3\pm 3a^{2}b+3a{b}^2\pm b^3$

Trigonometric Functions

The Six Basic Trigonometric Functions

Trigonometric Identities

${\cos }^2\theta +{\sin }^2\theta =1$

Addition Formulas
$\cos (A+B)=\cos A\cos B-\sin A\sin B$
$\sin (A+B)=\sin A\cos B+\cos A\sin B$

Double-Angle Formulas
$\cos 2\theta ={\cos }^2\theta -{\sin }^2\theta$
$\sin 2\theta =2\sin \theta \cos \theta$

Half-Angle Formulas
$co{s}^2\theta =\frac{1+\cos 2\theta }{2}$
$si{n}^2\theta =2$