Find the Reference Angle -(11pi)/18

$- \frac{11 π}{18}$

Step 1

Find an angle that is positive, less than $2 π$ , and coterminal with $- \frac{11 π}{18}$ .

Add $2 π$ to $- \frac{11 π}{18}$ .

$- \frac{11 π}{18} + 2 π$

The resulting angle of $\frac{25 π}{18}$ is positive and coterminal with $- \frac{11 π}{18}$ .

$\frac{25 π}{18}$

Step 2

Since the angle $π$ is in the third quadrant, subtract $π$ from $\frac{25 π}{18}$ .

$\frac{25 π}{18} - π$

Step 3

Simplify the result.

To write $- π$ as a fraction with a common denominator, multiply by $\frac{18}{18}$ .

$\frac{25 π}{18} - π \cdot \frac{18}{18}$

Combine fractions.

Combine $- π$ and $\frac{18}{18}$ .

$\frac{25 π}{18} + \frac{- π \cdot 18}{18}$

Combine the numerators over the common denominator.

$\frac{25 π - π \cdot 18}{18}$

Simplify the numerator.

Multiply $18$ by $- 1$ .

$\frac{25 π - 18 π}{18}$

Subtract $18 π$ from $25 π$ .

$\frac{7 π}{18}$