Hint: Divide the LHS by $\cos \theta $ and further use trigonometric formulas to convert the lower base into terms of $\sec \theta $ and $\tan \theta $ so that it could be cancelled out by the numerator. Use rationalizing to get to the answer.
Note: In these questions it is advised to simplify the LHS or the RHS according to their complexity of trigonometric functions . Sometimes proving LHS = RHS needs simplification on both sides of the equation. Remember to convert dissimilar trigonometric functions to get to the final result .