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Prove the trigonometric identity $\frac{\sin\left(x\right)}{\sec\left(x\right)+1}+\frac{\sin\left(x\right)}{\sec\left(x\right)-1}=2\cot\left(x\right)$

Step-by-step Solution

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Final Answer

true

Step-by-step Solution

Specify the solving method

1

Starting from the left-hand side (LHS) of the identity

$\frac{\sin\left(x\right)}{\sec\left(x\right)+1}+\frac{\sin\left(x\right)}{\sec\left(x\right)-1}$
2

Combine fractions with different denominator using the formula: $\displaystyle\frac{a}{b}+\frac{c}{d}=\frac{a\cdot d + b\cdot c}{b\cdot d}$

$\frac{\sin\left(x\right)\left(\sec\left(x\right)-1\right)+\sin\left(x\right)\left(\sec\left(x\right)+1\right)}{\left(\sec\left(x\right)+1\right)\left(\sec\left(x\right)-1\right)}$
3

The sum of two terms multiplied by their difference is equal to the square of the first term minus the square of the second term. In other words: $(a+b)(a-b)=a^2-b^2$.

$\frac{\sin\left(x\right)\left(\sec\left(x\right)-1\right)+\sin\left(x\right)\left(\sec\left(x\right)+1\right)}{\sec\left(x\right)^2-1}$
4

Factor the polynomial $\sin\left(x\right)\left(\sec\left(x\right)-1\right)+\sin\left(x\right)\left(\sec\left(x\right)+1\right)$ by it's greatest common factor (GCF): $\sin\left(x\right)$

$\frac{\sin\left(x\right)\left(2\sec\left(x\right)-1+1\right)}{\sec\left(x\right)^2-1}$
5

Subtract the values $1$ and $-1$

$\frac{\sin\left(x\right)2\sec\left(x\right)}{\sec\left(x\right)^2-1}$
6

Apply the trigonometric identity: $\sec\left(\theta \right)^2-1$$=\tan\left(\theta \right)^2$

$\frac{2\sin\left(x\right)\sec\left(x\right)}{\tan\left(x\right)^2}$
7

Applying the trigonometric identity: $\sin\left(\theta \right)\sec\left(\theta \right) = \tan\left(\theta \right)$

$\frac{2\tan\left(x\right)}{\tan\left(x\right)^2}$
8

Simplify the fraction by $\tan\left(x\right)$

$\frac{2}{\tan\left(x\right)}$
9

Applying the trigonometric identity: $\cot\left(\theta\right)=\frac{1}{\tan\left(\theta\right)}$

$2\cot\left(x\right)$
10

Since we have reached the expression of our goal, we have proven the identity

true

Final Answer

true

Explore different ways to solve this problem

Solving a math problem using different methods is important because it enhances understanding, encourages critical thinking, allows for multiple solutions, and develops problem-solving strategies. Read more

Prove from RHS (right-hand side)Express everything into Sine and Cosine

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