The problem is to simplify the expression $\tan(x) \cot(9^\circ) + \tan(5x)$. I assume the question is asking to simplify the expression and there is some equality sign hidden. Based on the identity for tangent of a sum, the problem seems to be leading to finding a value of $x$.

TrigonometryTrigonometric IdentitiesTangent FunctionCotangent FunctionSimplification
2025/4/21

1. Problem Description

The problem is to simplify the expression tan(x)cot(9)+tan(5x)\tan(x) \cot(9^\circ) + \tan(5x). I assume the question is asking to simplify the expression and there is some equality sign hidden. Based on the identity for tangent of a sum, the problem seems to be leading to finding a value of xx.

2. Solution Steps

Let's consider the tangent addition formula:
tan(a+b)=tan(a)+tan(b)1tan(a)tan(b)\tan(a+b) = \frac{\tan(a) + \tan(b)}{1 - \tan(a)\tan(b)}
We have the expression tan(x)cot(9)+tan(5x)\tan(x) \cot(9^\circ) + \tan(5x). Since cot(9)=1tan(9)\cot(9^\circ) = \frac{1}{\tan(9^\circ)}, we can rewrite the expression as:
tan(x)tan(9)+tan(5x)\frac{\tan(x)}{\tan(9^\circ)} + \tan(5x).
If the original problem asks to simplify the expression tan(x)tan(9)+tan(5x)\frac{\tan(x)}{\tan(9^\circ)} + \tan(5x), it is not clear what could be simplified further. Let us try to consider a scenario where this is equal to a tangent of a sum:
Let's suppose tan(x)tan(9)+tan(5x)=tan(a+b)\frac{\tan(x)}{\tan(9^\circ)} + \tan(5x) = \tan(a+b)
Assume we want to get an identity of the form tan(A)=tan(x)cot(9)+tan(5x)\tan(A) = \tan(x) \cot(9^\circ) + \tan(5x) for some AA.
Consider the tangent addition formula tan(a+b)=tan(a)+tan(b)1tan(a)tan(b)\tan(a+b) = \frac{\tan(a) + \tan(b)}{1 - \tan(a)\tan(b)}
We rewrite the expression as:
tan(x)cot(9)+tan(5x)=tan(x)tan(9)+tan(5x)\tan(x)\cot(9^{\circ}) + \tan(5x) = \frac{\tan(x)}{\tan(9^{\circ})} + \tan(5x)
Multiplying by tan(9)\tan(9^{\circ}), we get tan(x)+tan(5x)tan(9)\tan(x) + \tan(5x)\tan(9^{\circ})
If we set x=9x = 9^\circ, then the expression becomes tan(9)cot(9)+tan(59)=1+tan(45)=1+1=2\tan(9^\circ) \cot(9^\circ) + \tan(5\cdot 9^\circ) = 1 + \tan(45^\circ) = 1 + 1 = 2
Suppose the original question asked to evaluate the expression when x = 99^\circ.
Then, tan(9)cot(9)+tan(59)=tan(9)1tan(9)+tan(45)=1+1=2\tan(9^\circ) \cot(9^\circ) + \tan(5\cdot 9^\circ) = \tan(9^\circ) \frac{1}{\tan(9^\circ)} + \tan(45^\circ) = 1 + 1 = 2.
Let's assume we are supposed to find when tan(x)cot(9)+tan(5x)=tan(6x+9)\tan(x) \cot(9^\circ) + \tan(5x) = \tan(6x+9^\circ).
Using tan(6x+9)=tan(6x)+tan(9)1tan(6x)tan(9)=tan(x)cot(9)+tan(5x)=tan(x)tan(9)+tan(5x)\tan(6x+9^\circ) = \frac{\tan(6x) + \tan(9^\circ)}{1 - \tan(6x)\tan(9^\circ)} = \tan(x) \cot(9^\circ) + \tan(5x) = \frac{\tan(x)}{\tan(9^\circ)} + \tan(5x),
Then we would have
tan(6x)+tan(9)1tan(6x)tan(9)=tan(x)+tan(5x)tan(9)tan(9)\frac{\tan(6x) + \tan(9^\circ)}{1 - \tan(6x)\tan(9^\circ)} = \frac{\tan(x) + \tan(5x)\tan(9^\circ)}{\tan(9^\circ)}
tan(9)(tan(6x)+tan(9))=(1tan(6x)tan(9))(tan(x)+tan(5x)tan(9))\tan(9^\circ)(\tan(6x)+\tan(9^\circ)) = (1 - \tan(6x)\tan(9^\circ))(\tan(x) + \tan(5x)\tan(9^\circ))
tan(9)tan(6x)+tan2(9)=tan(x)+tan(5x)tan(9)tan(x)tan(6x)tan(9)tan(5x)tan(6x)tan2(9)\tan(9^\circ)\tan(6x) + \tan^2(9^\circ) = \tan(x) + \tan(5x)\tan(9^\circ) - \tan(x)\tan(6x)\tan(9^\circ) - \tan(5x)\tan(6x)\tan^2(9^\circ)
This becomes complex.

3. Final Answer

Without more context or constraints, it's impossible to determine a simplified answer. If x=9x=9^\circ, then the expression equals
2.

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