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**latus rectum: the chord through the focus of a
parabola parallel to the directrix. The **

** chord
through a focus of an ellipse perpendicular to the major axis.**

**law of cosines: c^{2} = a^{2}
+ b^{2} - 2abCosC**

**law of sines: a/sin A = b/sin B
= c/sin C**

**least common denominator: the least common denominator
of two fractions, a/b and c/d,**

**is the smallest number that contains both b and d as
factors.**

**least common multiple: the least common multiple
of two numbers, a and b, is the **

** smallest
number that contains both a and b as factors.**

**lemma: a theorem that is proved mainly as an aid in proving
another theorem.**

**like terms: two terms each of whose parts, with the exception
of their coefficients, is the **

** same.**

**line: a straight set of points that extends off into
infinity in both directions.**

**line segment: two points on a line, and all the points
between those two points.**

**logarithm: if y = b^{x}, then log_{b}
y = x.**

**logic: the study of sound reasoning.**