Find the Domain and Range y=-sec(2x)

$y = - \sec (2 x)$

Step 1

Set the argument in $\sec (2 x)$ equal to $\frac{π}{2} + π n$ to find where the expression is undefined.

$2 x = \frac{π}{2} + π n$ , for any integer $n$

Step 2

Divide each term in $2 x = \frac{π}{2} + π n$ by $2$ and simplify.

Divide each term in $2 x = \frac{π}{2} + π n$ by $2$ .

$\frac{2 x}{2} = \frac{\frac{π}{2}}{2} + \frac{π n}{2}$

Simplify the left side.

Cancel the common factor of $2$ .

Cancel the common factor.

$\frac{2 x}{2} = \frac{\frac{π}{2}}{2} + \frac{π n}{2}$

Divide $x$ by $1$ .

$x = \frac{\frac{π}{2}}{2} + \frac{π n}{2}$

Simplify the right side.

Simplify each term.

Multiply the numerator by the reciprocal of the denominator.

$x = \frac{π}{2} \cdot \frac{1}{2} + \frac{π n}{2}$

Multiply $\frac{π}{2} \cdot \frac{1}{2}$ .

Multiply $\frac{π}{2}$ by $\frac{1}{2}$ .

$x = \frac{π}{2 \cdot 2} + \frac{π n}{2}$

Multiply $2$ by $2$ .

$x = \frac{π}{4} + \frac{π n}{2}$

Step 3

The domain is all values of $x$ that make the expression defined.

Set-Builder Notation:

${x | x \neq \frac{π}{4} + \frac{π n}{2}}$ , for any integer $n$

Step 4

The range is the set of all valid $y$ values. Use the graph to find the range.

Interval Notation:

$(- \infty, - 1] \cup [1, \infty)$

Set-Builder Notation:

${y | y \leq - 1, y \geq 1}$

Step 5

Determine the domain and range.

Domain: ${x | x \neq \frac{π}{4} + \frac{π n}{2}}$ , for any integer $n$

Range: $(- \infty, - 1] \cup [1, \infty), {y | y \leq - 1, y \geq 1}$

Step 6