Derivatives of Constant Multiples

Example:
B(z) = 6*(cos(z))4

The first thing to notice when finding the derivative of this function is that it is the product of a constant and another function, as shown in color below:

B(z) = 6 (cos(z))4

The Derivative Rule for Constant Multiples:

The derivative of a constant multiple is the constant times thederivative of the function.
If
  z = c ( f(x) )
then the derivative of z is
  z' = ( c f(x) )'
    = c f '(x)

So our example,

B(z) = 6 (cos(z))4
we can think of as
B(z) = c f(z)
So the derivative is
B '(z) = ( c f(z) )'
  = c f '(z)  
  = 6 ((cos(z))4)'  
and we just need to know the derivative on the right-hand side of the equation. In this case this is
(cos(z))4 = (-1)*4*(cos(z))3 sin(z) (by the chain rule)
so the finished derivative is
B '(z) = 6 ( (-1)*4*(cos(z))3 sin(z) )
  = (-24)*(cos(z))3 sin(z)
[]


additional explanation for the derivative of constant multiples
see another derivative of constant multiples example
practice gateway test
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Comments to Gavin LaRose
glarose@umich.edu
©2001 Gavin LaRose, University of Michigan Math Dept.