Math 2.0

Special functions Proposition

Derivative of tangent

Builds on Tangent functionQuotient ruleDerivative of sineDerivative of cosinePythagorean trigonometric identity

Statement

The tangent function is differentiable at every xx with cos⁡x≠0\cos x \ne 0, and tan⁡′(x)=1cos⁡2x=1+tan⁡2x.\tan'(x) = \frac{1}{\cos^2 x} = 1 + \tan^2 x.

Remarks

The quotient rule gives tan⁡′=cos⁡⋅cos⁡−sin⁡⋅(−sin⁡)cos⁡2\tan' = \frac{\cos \cdot \cos - \sin \cdot (-\sin)}{\cos^2}. The Pythagorean identity turns the numerator into 11. The derivative is positive. So tan⁡\tan is strictly increasing on (−π/2,π/2)(-\pi/2, \pi/2). Mathlib states it as Real.hasDerivAt_tan.

Reading path

To understand this page from the ground up, read these 64 pages in order. The foundations come first.

  1. Limit point of a set definition
  2. Local maximum definition
  3. Sequence definition
  4. Limit of a function definition
  5. Local minimum definition
  6. Real sequence definition
  7. Subsequence definition
  8. Continuity at a point definition
  9. Derivative definition
  10. Bounded sequence definition
  11. Cauchy sequence definition
  12. Geometric sequence definition
  13. Limit of a sequence definition
  14. Monotone sequence definition
  15. Series definition
  16. Continuous function definition
  17. Differentiable function definition
  18. Fermat's theorem on stationary points statement
  19. Limit superior definition
  20. Cauchy sequences are bounded statement
  21. Sum of a finite geometric series statement
  22. Monotone convergence theorem for sequences statement
  23. Every sequence has a monotone subsequence statement
  24. Convergent sequence definition
  25. Pointwise convergence definition
  26. Squeeze theorem statement
  27. Partial sum definition
  28. Power series definition
  29. Differentiable functions are continuous statement
  30. Bolzano–Weierstrass theorem statement
  31. The sequence r^n tends to zero for |r| < 1 example
  32. Radius of convergence definition
  33. Convergent series definition
  34. Uniform convergence definition
  35. Sine and cosine definition
  36. Boundedness theorem statement
  37. Product rule statement
  38. Reciprocal rule statement
  39. Cauchy criterion for sequences statement
  40. Uniform convergence on a set definition
  41. Absolute convergence definition
  42. Tangent function definition
  43. A series of nonnegative terms converges iff its partial sums are bounded statement
  44. Series of functions definition
  45. Sum of a series definition
  46. Extreme value theorem statement
  47. Quotient rule statement
  48. Uniformly Cauchy sequence of functions definition
  49. Geometric series example
  50. Comparison test statement
  51. Rolle's theorem statement
  52. Root test statement
  53. Weierstrass M-test statement
  54. Mean value theorem statement
  55. Cauchy–Hadamard theorem statement
  56. Power series converge uniformly on smaller discs inside the radius of convergence statement
  57. A function with zero derivative is constant statement
  58. Uniform convergence of derivatives allows term-by-term differentiation statement
  59. Term-by-term differentiation statement
  60. Power series are differentiable inside the radius of convergence statement
  61. Derivative of cosine statement
  62. Derivative of sine statement
  63. Pythagorean trigonometric identity statement
  64. Derivative of tangent statement

Where this leads

2 pages build on this one.

Further reading

  1. Web https://en.wikipedia.org/wiki/Differentiation_of_trigonometric_functions, From the quotient rule
About this page
Tag0SAMR34WXC
URIm2://0SAMR34WXC
Kindstatement, proposition
WritingW0 stub
MSC33B10, 26A24
StatusThis copy of the site has no build data. Run m2 status 0SAMR34WXC.
UsesTangent function, Quotient rule, Derivative of sine, Derivative of cosine, Pythagorean trigonometric identity

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