sentences:  Differentiation of trigonometric functions
  
  The differentiation of trigonometric functions is the mathematical process of finding the derivative of a trigonometric function, or its rate of change with respect to a variable.For example, the derivative of the sine function is written sin′("a") = cos("a"), meaning that the rate of change of sin("x") at a particular angle "x = a" is given by the cosine of that angle.