# Find d/dx?

##### 1 Answer

Feb 7, 2018

The answer is

#### Explanation:

Where

#d/dx int_a^xf(t)dt = f(x)#

Therefore, using the chain rule, we can say that:

#d/dx int_a^uf(t)dt = f(u) * (du)/dx#

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

In this case, we can let

Therefore:

#d/dx int_1^(3x) cos^2(t)dt = cos^2(3x) * d/dx(3x)#

#= cos^2(3x) * 3#

#= 3cos^2(3x)#

*Final Answer*