The problem consists of four parts: 1. Verify the equality $\sqrt{3 + 2\sqrt{2}} = 1 + \sqrt{2}$.
AlgebraRadicalsQuadratic EquationsQuadratic InequalitiesTrigonometryTrigonometric EquationsTrigonometric Inequalities
2025/4/14
1. Problem Description
The problem consists of four parts:
1. Verify the equality $\sqrt{3 + 2\sqrt{2}} = 1 + \sqrt{2}$.
2. Solve the quadratic equation $2x^2 + (1 - \sqrt{2})x - \frac{\sqrt{2}}{2} = 0$ and the inequality $2x^2 + (1 - \sqrt{2})x - \frac{\sqrt{2}}{2} > 0$ in the real numbers.
3. Find the solutions of the trigonometric equation $2\cos^2x + (1 - \sqrt{2})\cos x - \frac{\sqrt{2}}{2} = 0$. Represent the solutions on the unit circle.
4. Find the solutions in $[0, 2\pi]$ of the inequality $2\cos^2x + (1 - \sqrt{2})\cos x - \frac{\sqrt{2}}{2} > 0$. Represent the solutions on the unit circle.
2. Solution Steps
1. Verify the equality:
. Thus .
2. Solve the quadratic equation and inequality:
The equation is .
We can multiply by 2 to get .
The discriminant is .
Thus the solutions are .
.
.
Now, consider the inequality .
Since the leading coefficient is positive, the parabola opens upward. The inequality is satisfied when or .
3. Solve the trigonometric equation:
Let . Then the equation becomes .
The solutions are and .
So or .
If , then , .
If , then , .
The solutions are for .
4. Solve the trigonometric inequality in $[0, 2\pi]$:
.
Let . Then we have . The solutions are or .
So or .
when .
when .
Thus, the solution is .