Bernoulli Trials P ( E ) = n k p ​ k ( 1 - p ) ​ n - k Cauchy-Schwarz Inequality k = 1 n a k ​ b k ​ ​ 2 ≤ k = 1 n a k 2 k = 1 n b k 2 Cauchy Formula f ( z )   · Ind γ ​ ( z ) = 1 2 π i γ ​ f ( ξ ) ξ - z   d ξ Cross Product V 1 ​ × V 2 ​ = i j k ∂ X ∂ u ∂ Y ∂ u 0 ∂ X ∂ v ∂ Y ∂ v 0 Vandermonde Determinant 1 1 ⋯ 1 v 1 ​ v 2 ​ ⋯ v n ​ v 1 2 v 2 2 ⋯ v n 2 ⋮ ⋮ ⋱ ⋮ v 1 n - 1 v 2 n - 1 ⋯ v n n - 1 = 1 ≤ i < j ≤ n ​ ( v j ​ - v i ​ ) Lorenz Equations x ​ = σ ( y - x ) y ​ = ρ x - y - x z z ​ = - β z + x y Maxwell's Equations ∇ ​ × B ​ -   1 c   ∂ ​ E ​ ∂ ​ t = 4 π c   j ​ ∇ ​ · E ​ = 4 π ρ ∇ ​ × E ​   +   1 c   ∂ ​ B ​ ∂ ​ t = 0 ​ ∇ ​ · B ​ = 0 Einstein Field Equations R μ ν ​ - 1 2   g μ ν ​   R = 8 π G c ​ 4   T μ ν ​ Ramanujan Identity 1 ( φ 5 - φ ) e ​ 25 π = 1 + e ​ - 2 π 1 + e ​ - 4 π 1 + e ​ - 6 π 1 + e ​ - 8 π 1 + … Another Ramanujan identity k = 1 ∞ 1 2 ​ ⌊ k · ​ φ ⌋ = 1 2 ​ 0 + 1 2 ​ 1 + ⋯ Rogers-Ramanujan Identity 1 + k = 1 ∞ q ​ k ​ 2 + k ( 1 - q ) ( 1 - q ​ 2 ) ⋯ ( 1 - q ​ k ) = j = 0 ∞ 1 ( 1 - q ​ 5 j + 2 ) ( 1 - q ​ 5 j + 3 ) ,       f o r   | q | < 1 . Commutative Diagram H ← K ↓ ​ ↑ H → K