Derivatives of Constant Multiples

Example:
L(q) = 10*(tan(q))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:

L(q) = 10 (tan(q))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,

L(q) = 10 (tan(q))4
we can think of as
L(q) = c f(q)
So the derivative is
L '(q) = ( c f(q) )'
  = c f '(q)  
  = 10 ((tan(q))4)'  
and we just need to know the derivative on the right-hand side of the equation. In this case this is
(tan(q))4 = 4*(tan(q))3 (1 / (cos(q))2) (by the chain rule)
so the finished derivative is
L '(q) = 10 ( 4*(tan(q))3 (1 / (cos(q))2) )
  = 40*(tan(q))3 (1 / (cos(q))2)
[]


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.