y = cos³x tan x

The right hand side is a product of (cos x)³ and (tan x).

Now (cos x)³ is a power of a function and so we use Differentiating Powers of a Function:

With u = cos x, we have:

Now, from our rules above, we have:

Using the Product Rule and Properties of tan x, we have:

We need to determine if this expression creates a true statement when we substitute it into the LHS of the equation given in the question.

We have shown that it is true.