Solve each equation for x, where x is restricted to the given interval.
y = ― 2 cos 5x , for x in [0, π/5]

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Identify the given equation: $y = -2 \cos 5x$ and the interval for $x$ is $[0, \frac{\pi}{5}]$.

Since the problem asks to solve for $x$, determine the value of $y$ you want to solve for. If a specific $y$ value is given, set $-2 \cos 5x = y$; if not, clarify the target $y$ value or condition.

Isolate the cosine term by dividing both sides by $-2$: $\cos 5x = -\frac{y}{2}$.

Use the inverse cosine function to solve for \$5x$: $5x = \arccos\left(-\frac{y}{2}\right)$ and consider the general solutions for cosine within the interval.

Divide the solutions for \$5x$ by 5 to find $x$, then check which solutions lie within the interval $[0, \frac{\pi}{5}]$.

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주요 개념

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Solving Trigonometric Equations

Solving trigonometric equations involves finding all values of the variable that satisfy the equation within a given interval. This often requires isolating the trigonometric function and using inverse functions or known angle values to determine solutions.

Properties of the Cosine Function

The cosine function is periodic with period 2π and ranges between -1 and 1. Understanding its behavior, including symmetry and key values at standard angles, helps in solving equations involving cosine, especially when the argument is multiplied by a constant.

Interval Restrictions and Domain Considerations

When solving equations on a restricted interval, only solutions within that domain are valid. This requires checking all possible solutions from the general solution and selecting those that lie within the specified interval, ensuring the answer meets the problem’s constraints.

Solve each equation for x, where x is restricted to the given interval.y = ― 2 cos 5x , for x in [0, π/5]