Phi (/faɪ/; uppercase Φ, lowercase φ or ϕ; Ancient Greek: ϕεῖ pheî [pʰéî̯]; Modern Greek: φι fi [fi]) is the twenty-first letter of the Greek alphabet...

ᴺ ᴻ ᴼ ᴽ ᴾ ᴿ ᵀ ᵁ ᵂ ᵃ ᵄ ᵅ ᵆ ᵇ ᵈ ᵉ ᵊ ᵋ ᵌ ᵍ ᵏ ᵐ ᵑ ᵒ ᵓ ᵖ ᵗ ᵘ ᵚ ᵛ, Greek ᵝ ᵞ ᵟ ᵠ ᵡ, Cyrillic ᵸ, other ᵎ ᵔ ᵕ ᵙ ᵜ. These are intended to indicate secondary articulation...

prime to n. It is written using the Greek letter phi as φ ( n ) {\displaystyle \varphi (n)} or ϕ ( n ) {\displaystyle \phi (n)} , and may also be called...

a linear expression, as in: 3 φ 3 − 5 φ 2 + 4 = 3 ( φ 2 + φ ) − 5 φ 2 + 4 = 3 [ ( φ + 1 ) + φ ] − 5 ( φ + 1 ) + 4 = φ + 2 ≈ 3.618033. {\displaystyle...

latitude ϕ to the equator is given by (ϕ in radians) m ( ϕ ) = ∫ 0 ϕ M ( ϕ ′ ) d ϕ ′ = a ( 1 − e 2 ) ∫ 0 ϕ ( 1 − e 2 sin 2 ⁡ ϕ ′ ) − 3 2 d ϕ ′ {\displaystyle...

A ϕ ( z ) ( ρ + d ρ ) d ϕ − A ϕ ( z + d z ) ( ρ + d ρ ) d ϕ + A z ( ϕ + d ϕ ) d z − A z ( ϕ ) d z ( ρ + d ρ ) d ϕ d z = − ∂ A ϕ ∂ z + 1 ρ ∂ A z ∂ ϕ {\displaystyle...

position of a given point in space is specified by three numbers, (r, θ, φ): the radial distance of the radial line r connecting the point to the fixed...

cos ⁡ φ ,   sin ⁡ φ ) + 2 r ˙ φ ˙ ( − sin ⁡ φ ,   cos ⁡ φ ) + r φ ¨ ( − sin ⁡ φ ,   cos ⁡ φ ) − r φ ˙ 2 ( cos ⁡ φ ,   sin ⁡ φ ) = ( r ¨ − r φ ˙ 2 ) r...

becomes 1 + φ + φ 2 + ⋯ + φ n − ( 1 + ψ + ψ 2 + ⋯ + ψ n ) = φ n + 1 − 1 φ − 1 − ψ n + 1 − 1 ψ − 1 = φ n + 1 − 1 − ψ − ψ n + 1 − 1 − φ = − φ n + 2 + φ + ψ n...

the following form: if X is a random variable and φ is a convex function, then φ ( E ⁡ [ X ] ) ≤ E ⁡ [ φ ( X ) ] . {\displaystyle \varphi (\operatorname...