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Cofunction Identities

Trig identities showing the relationship between sine and cosine, tangent and cotangent, and secant and cosecant. The value of a trig function of an angle equals the value of the cofunction of the complement of the angle.

 

Cofunction Identities, radians

  Cofunction Identities, degrees
 

sin (90° – x) = cos x

cos (90° – x) = sin x

  tan (90° – x) = cot x cot (90° – x) = tan x
  sec (90° – x) = csc x csc (90° – x) = sec x

 


  this page updated 28-jul-14
Mathwords: Terms and Formulas from Algebra I to Calculus
written, illustrated, and webmastered by Bruce Simmons
NCTM Web Bytes December 2004 Web Bytes March 2005 Web Bytes