We will gossip about sines and co-sines before we die.
"The Odd Women" by George Gissing
Define the terms sine, co-sine, tangent, and co-tangent.
"Scientific American Supplement, No. 561, October 2, 1886" by Various
Inventor of the terms co-sine, co-tangent, etc.
"A Brief Handbook of English Authors" by Oscar Fay Adams
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For D ≡ 1 (mod 4) it is also an algebraic integer when a and b as special values of (co)sine at rational angles. Z. (Note e.g. that 1 Observation (Quadratic Irrationalities). i) Let x be a quadratic integer such that |x| < 2 and |x| < 2.
When is the (co)sine of a rational angle equal to a rational number?
The zeroes found are indeed special values of (co)sine at rational angles.
When is the (co)sine of a rational angle equal to a rational number?
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