Answer:
is used to prove the given equation.
Step-by-step explanation:
We have given an equation:

We will consider right hand side first
tan x can be written as:

So, on substituting tan x in the left hand side of the given equation we get:

Cancel common term from denominator and numerator which is cosx we get

And we have an identity:


Hence, right hand side is equal to
.
Looks correct. :)...........
The rule for quotients of similar bases with different exponents is:
(a^c)/(a^b)=a^(c-b) in this case:
15^18/(15^3)=15^15