Derivatives of  Trigonometric Functions
If y = sin x, then y’ = cos x For example: If given y = 3x - 5 sinx  and asked to find y’ y’ = 3 - 5 cos x
If y = cos x, then y’ = -sin x For example: If given y = 7x 2  + 2cos x and asked to find y’ you would get y’ = 14x - 2sinx
So you already know the derivatives of sin x and cos x.  Here are the rest: y  y’ sin x cos x cos x -sin x tan x sec 2 x cot x -csc 2 x sec x sec x tan x csc x -csc x cot x
HINTS: All the derivatives of the  “co”-functions are negatives. They are also the opposite of whatever they are the co-function of. For example: The derivative of tan x is sec 2 x, so the derivative of the co-function of tan x, cot x, is negative and the opposite of sec x, so you get -csc 2 x.
Examples: y = 3 csc x y’ = -3 csc x cot x y = 5x 3  + tan x y’ = 15x 2  + sec 2 x
Product Rule and Quotient Rule still apply. y = x 2  sin x y’ = uv’ + vu’ y’ = x 2  cos x + sin x · 2x or y’ = x 2  cos x + 2x sin x
Do page 146 (1 - 10) for HW

3.5 Derivatives Of Trig Functions

  • 1.
    Derivatives of Trigonometric Functions
  • 2.
    If y =sin x, then y’ = cos x For example: If given y = 3x - 5 sinx and asked to find y’ y’ = 3 - 5 cos x
  • 3.
    If y =cos x, then y’ = -sin x For example: If given y = 7x 2 + 2cos x and asked to find y’ you would get y’ = 14x - 2sinx
  • 4.
    So you alreadyknow the derivatives of sin x and cos x. Here are the rest: y y’ sin x cos x cos x -sin x tan x sec 2 x cot x -csc 2 x sec x sec x tan x csc x -csc x cot x
  • 5.
    HINTS: All thederivatives of the “co”-functions are negatives. They are also the opposite of whatever they are the co-function of. For example: The derivative of tan x is sec 2 x, so the derivative of the co-function of tan x, cot x, is negative and the opposite of sec x, so you get -csc 2 x.
  • 6.
    Examples: y =3 csc x y’ = -3 csc x cot x y = 5x 3 + tan x y’ = 15x 2 + sec 2 x
  • 7.
    Product Rule andQuotient Rule still apply. y = x 2 sin x y’ = uv’ + vu’ y’ = x 2 cos x + sin x · 2x or y’ = x 2 cos x + 2x sin x
  • 8.
    Do page 146(1 - 10) for HW