cos 2x + 1 / sin 2x = cot x

Question image

Understand the Problem

The question is asking to solve the trigonometric equation given in the image, which involves manipulating and simplifying trigonometric identities to find the values of x that satisfy the equation.

Answer

The solution holds true for any $x$ where both sides are defined, except where $\sin x = 0$.
Answer for screen readers

The solution to the equation is that it holds true for any $x$ where both sides are defined, except where $\sin x = 0$.

Steps to Solve

  1. Rewrite cotangent in terms of sine and cosine

Recall that the cotangent function can be expressed as: $$ \cot x = \frac{\cos x}{\sin x} $$

  1. Cross-multiply

Rearranging the equation gives: $$ \cos 2x + 1 = \cot x \cdot \sin 2x $$

So we can rewrite it as: $$ \cos 2x + 1 = \frac{\cos x}{\sin x} \cdot \sin 2x $$

  1. Substitute using the double angle identity for sine

Using the identity $\sin 2x = 2 \sin x \cos x$: $$ \cos 2x + 1 = \frac{\cos x}{\sin x} \cdot 2 \sin x \cos x $$

This simplifies to: $$ \cos 2x + 1 = 2 \cos^2 x $$

  1. Use the double angle identity for cosine

Recall that $\cos 2x = 2 \cos^2 x - 1$. Substitute this into the equation: $$ 2 \cos^2 x - 1 + 1 = 2 \cos^2 x $$

This simplifies to: $$ 2 \cos^2 x = 2 \cos^2 x $$

  1. Conclude

Since we have demonstrated an identity, it means the original equation holds for any $x$ where both sides are defined.

The solution to the equation is that it holds true for any $x$ where both sides are defined, except where $\sin x = 0$.

More Information

This equation leverages trigonometric identities and properties, demonstrating that some equations can hold universally under certain conditions, specifically those that don’t cause division by zero.

Tips

  • Forgetting to consider the restrictions on $x$ where $\sin x = 0$, which leads to undefined cotangent.
  • Misapplying trigonometric identities can lead to incorrect conclusions.

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