Clue | Letter |

Lagrange multipliers in calculus, or eigenvalues in linear algebra | |

number of positive integers less than and coprime to a given integer | |

coefficient of the real component of a complex number | |

in number theory, the sum of the divisors of a positive integer | |

representation of a group, or radius in spherical polar coordinates | |

change in a quantity, usually as it relates to change in another quantity | |

character in representation theory, or chromatic number in graph theory | |

the Möbius function, which always takes on a value of -1, 0, or 1 | |

the least ordinal which the reals cannot map onto surjectively | |

extension of the factorial function to complex numbers | |

a summation, has a subscript and sometimes a superscript | |

probably the most underused Greek letter, not sure why it isn't more common | |

looks too much like a 1 to be used | |

looks too much like a 0 to be used | |

looks too much like a V to be used | |

looks too much like a U to be used | |

a bit too long to be used as a mathematical variable, methinks | |