I came across a function where we have to find **n** where they give us two separate values **a** and **b**.

The function is:

f(= 2 x $7^ {n/2} $ x cos()nnθ) +nx $4^n$ , whereθ= $tan^{-1}$ ($frac32$)

=> the **3 is square rooted** in the theta function, I couldn’t figure out how to do that with Math Jax.

The summation is:

$sum_{n=a}^{n=b} f(n)$

With the values of **a** and **b**, I need to figure out how to get the value of **n** given by the function and series.