ButtonBox[boxes] is a low-level box construct that represents a button in a notebook expression.
EllipticExp[u, {a, b}] is the inverse for EllipticLog. It produces a list {x, y} such that u == EllipticLog[{x, y}, {a, b}].
EllipticLog[{x, y}, {a, b}] gives the generalized logarithm associated with the elliptic curve y^2 = x^3 + a x^2 + b x.
Haversine[z] gives the haversine function hav(z).
Hypergeometric0F1Regularized[a, z] is the regularized confluent hypergeometric function \[Null]_0 F_1 (a; z)/\[CapitalGamma](a).
Hypergeometric1F1Regularized[a, b, z] is the regularized confluent hypergeometric function \[Null]_1 F_1 (a; b; z)/\[CapitalGamma](b).
InterpretationBox[boxes, expr] is a low-level box construct that displays as boxes but is interpreted on input as expr.
Log10
(Built-in Mathematica Symbol) Log10[x] gives the base-10 logarithm of x.
MathieuCharacteristicA[r, q] gives the characteristic value a_r for even Mathieu functions with characteristic exponent r and parameter q.
MathieuCharacteristicB[r, q] gives the characteristic value b_r for odd Mathieu functions with characteristic exponent r and parameter q.