Sine, cosine & (this)

noun

1. An abrupt change of course digression

   "the speaker went off on a tangent"

2. The trigonometric function that for an acute angle is the ratio between the leg opposite to the angle when it is considered part of a right triangle and the leg adjacent
3. A trigonometric function that is equal to the sine divided by the cosine for all real numbers θ for which the cosine is not equal to zero and is exactly equal to the tangent of an angle of measure θ in radians
4. A line that is tangent
5. A small upright flat-ended metal pin at the inner end of a clavichord key that strikes the string to produce the tone

adjective

1. Meeting a curve or surface in a single point if a sufficiently small interval is considered

   "straight line tangent to a curve"

2. Diverging from an original purpose or course irrelevant

   "tangent remarks"

noun

1. The plane through a point of a surface that contains the tangent lines to all the curves on the surface through the same point

idiom

1. To start talking about something that is only slightly or indirectly related to the original subject

   "She went off on a tangent about what happened to her last summer."

noun

1. The inverse function of the tangent

   "if y is the tangent of θ, then θ is the arctangent of y"