# How do you find the derivative of #f(x)= cos^(4) (5x)#?

##### 1 Answer

Nov 1, 2016

#### Answer:

Remember that

#### Explanation:

# = 4(cos(5x))^3 * [sin(5x)*d/dx(5x)]#

# = 4(cos(5x))^3 * [sin(5x)*(5)]#

# = 20cos^3(5x) sin(5x)#