Math Problem Statement

\sin\sqrt2 $$$$ x $$$$ -\cos\frac{x}{2} $$$$ =0

Solution

You are given the equation:

sin(2x)cos(x2)=0\sin(\sqrt{2}x) - \cos\left(\frac{x}{2}\right) = 0

To solve this, we want to find values of xx that satisfy the equation. Let's follow these steps:

Step 1: Isolate one of the trigonometric functions

Rearrange the equation:

sin(2x)=cos(x2)\sin(\sqrt{2}x) = \cos\left(\frac{x}{2}\right)

Step 2: Use a trigonometric identity

Recall the identity cos(θ)=sin(π2θ)\cos(\theta) = \sin\left(\frac{\pi}{2} - \theta\right). So, we can rewrite the equation as:

sin(2x)=sin(π2x2)\sin(\sqrt{2}x) = \sin\left(\frac{\pi}{2} - \frac{x}{2}\right)

Step 3: Solve the sine equation

For sinA=sinB\sin A = \sin B, the general solution is:

A=B+2kπorA=πB+2kπforkZA = B + 2k\pi \quad \text{or} \quad A = \pi - B + 2k\pi \quad \text{for} \quad k \in \mathbb{Z}

Thus, we have two cases:

  1. 2x=π2x2+2kπ\sqrt{2}x = \frac{\pi}{2} - \frac{x}{2} + 2k\pi
  2. 2x=π(π2x2)+2kπ\sqrt{2}x = \pi - \left(\frac{\pi}{2} - \frac{x}{2}\right) + 2k\pi

Step 4: Solve each case

Case 1: 2x=π2x2+2kπ\sqrt{2}x = \frac{\pi}{2} - \frac{x}{2} + 2k\pi

Multiply through by 2 to eliminate the fraction:

22x=πx+4kπ2\sqrt{2}x = \pi - x + 4k\pi

Now, solve for xx:

22x+x=π+4kπ2\sqrt{2}x + x = \pi + 4k\pi

Factor out xx:

x(22+1)=π(1+4k)x(2\sqrt{2} + 1) = \pi(1 + 4k)

Thus,

x=π(1+4k)22+1x = \frac{\pi(1 + 4k)}{2\sqrt{2} + 1}

Case 2: 2x=π(π2x2)+2kπ\sqrt{2}x = \pi - \left(\frac{\pi}{2} - \frac{x}{2}\right) + 2k\pi

Simplify the right-hand side:

2x=ππ2+x2+2kπ\sqrt{2}x = \pi - \frac{\pi}{2} + \frac{x}{2} + 2k\pi

2x=π2+x2+2kπ\sqrt{2}x = \frac{\pi}{2} + \frac{x}{2} + 2k\pi

Multiply through by 2 to eliminate the fraction:

22x=π+x+4kπ2\sqrt{2}x = \pi + x + 4k\pi

Now, solve for xx:

22xx=π(1+4k)2\sqrt{2}x - x = \pi(1 + 4k)

Factor out xx:

x(221)=π(1+4k)x(2\sqrt{2} - 1) = \pi(1 + 4k)

Thus,

x=π(1+4k)221x = \frac{\pi(1 + 4k)}{2\sqrt{2} - 1}

Final Answer

The solutions to the equation are:

x=π(1+4k)22+1orx=π(1+4k)221,kZx = \frac{\pi(1 + 4k)}{2\sqrt{2} + 1} \quad \text{or} \quad x = \frac{\pi(1 + 4k)}{2\sqrt{2} - 1}, \quad k \in \mathbb{Z}

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Trigonometric Equations
Sine and Cosine Identities

Formulas

\( \cos(\theta) = \sin\left(\frac{\pi}{2} - \theta\right) \)
General solution of sine equation: \( \sin A = \sin B \Rightarrow A = B + 2k\pi \text{ or } A = \pi - B + 2k\pi, k \in \mathbb{Z} \)

Theorems

Sine-Cosine Complementary Angle Identity

Suitable Grade Level

Grades 11-12 or College-Level Mathematics