Mathematics encompasses a wide range of fields, each with its own set of important formulae. Here are some key formulae from various branches:
Algebra
- Quadratic Formula: For the quadratic equation \( ax^2 + bx + c = 0 \), \[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \]
- Binomial Theorem: For any positive integer \( n \), \[ (a + b)^n = \sum_{k=0}^{n} \binom{n}{k} a^{n-k} b^k \]
Geometry
- Pythagorean Theorem: In a right triangle, the square of the hypotenuse \( c \) is equal to the sum of the squares of the other two sides \( a \) and \( b \), \[ c^2 = a^2 + b^2 \]
- Area of a Circle: Given a circle with radius \( r \), \[ \text{Area} = \pi r^2 \]
- Circumference of a Circle: \[ \text{Circumference} = 2\pi r \]
Trigonometry
- Sine, Cosine, Tangent: For a right triangle with angle \( \theta \), \[ \sin \theta = \frac{\text{opposite}}{\text{hypotenuse}} \] \[ \cos \theta = \frac{\text{adjacent}}{\text{hypotenuse}} \] \[ \tan \theta = \frac{\text{opposite}}{\text{adjacent}} \]
- Pythagorean Identity: \[ \sin^2\theta + \cos^2\theta = 1 \]
Calculus
- Derivative of a Function: The derivative of a function \( f(x) \) with respect to \( x \) is defined as, \[ f'(x) = \lim_{h \to 0} \frac{f(x + h) - f(x)}{h} \]
- Fundamental Theorem of Calculus: \[ \int_a^b f(x) \, dx = F(b) - F(a) \] where \( F \) is an antiderivative of \( f \), i.e., \( F'(x) = f(x) \).
Probability and Statistics
- Bayes' Theorem: For events \( A \) and \( B \), \[ P(A|B) = \frac{P(B|A) P(A)}{P(B)} \]
- Standard Deviation**: For a set of data \( x_1, x_2, \ldots, x_n \) with mean \( \mu \), \[ \sigma = \sqrt{\frac{1}{n} \sum_{i=1}^{n} (x_i - \mu)^2} \]
Linear Algebra
- Matrix Multiplication: For matrices \( A \) and \( B \), \[ (AB)_{ij} = \sum_{k} A_{ik} B_{kj} \]
- Determinant of a 2x2 Matrix: For matrix \( A = \begin{pmatrix} a & b \\ c & d \end{pmatrix} \), \[ \text{det}(A) = ad - bc \]
Number Theory
- Euclidean Algorithm: To find the greatest common divisor (gcd) of two integers \( a \) and \( b \), \[ \text{gcd}(a, b) = \text{gcd}(b, a \mod b) \]
- Fermat's Little Theorem: If \( p \) is a prime number and \( a \) is an integer not divisible by \( p \), then \[ a^{p-1} \equiv 1 \pmod{p} \]
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