Derivative of Cosine

Suggested Prerquesites:

Definition of the Derivative, Useful Trigonometric Identities,

We'll deduce the derivative of cos(x) directly from the definition of the derivitive.

Then, since and

Does this make sense? Cosine is increasing where sine is negative and decreasing where sine is positive. The tangent lines to cosine are flat where sine is zero. So, it does make sense.

Exercises:

  3. Prove that

    (Hint: use double angle formulas)

Solutions to the exercises | Back to the Calculus page | Back to the World Web Math top page
jjnichol@mit.edu
Last modified 23 June 1997