Mnemonic Device:
 Two Old Angels Skipped Over Heaven, Carrying Ancient Harps
Explanation: the equations for Tangent, Sine, and Cosine.

O stands for opposite, A stands for adjacent, and H stands for hypotenuse.
 Tangent = Opposite/Adjacent (Two Old Angels)
 Sine = Opposite/Hypotenuse (Skipped Over Heaven)
 Cosine = Adjacent/Hypotenuse (Carrying Ancient Harps)
Variation:

Two Old Aunts, Sitting On Horseback, Catching A Husband. Any Old Time, Husbands Are Caught, Hail Or Shine.
 Tangent = Opposite/Adjacent (Two Old Aunts)
Sine = Opposite/Hypotenuse (Sitting On Horseback)
Cosine = Adjacent/Hypotenuse (Catching A Husband) 
Inverse functions:
 Cosine = Adjacent/Hypotenuse (Husbands Are Caught)
 Tangent = Opposite/Adjacent (Any Old Time)
 Sine = Opposite/Hypotenuse (Hail Or Shine)
 Tangent = Opposite/Adjacent (Two Old Aunts)
Additional Note: We are looking for additional information for the variation of this mnemonic (inverse functions). Do you have suggestions or corrections for this? If so, please submit a comment!
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