Identify the reference angle \( \phi \) for each given angle, \( \theta \). When \( \theta=300^{\circ}, \phi=60 \) degrees. When \( \theta=225^{\circ}, \phi=\square \) degrees. When \( \theta=480^{\circ}, \phi=60 \) degrees. When \( \theta=-210^{\circ}, \phi=30 \) degrees. DONE \( \boldsymbol{\text { DO }} \)

To find the reference angle \( \phi \) for \( \theta = 225^{\circ} \), first, recognize that angles in the second and third quadrants are measured differently. Since \( 225^{\circ} \) is in the third quadrant, you subtract \( 180^{\circ} \) from it: \[ \phi = 225^{\circ} - 180^{\circ} = 45^{\circ}. \] So, for \( \theta = 225^{\circ} \), the reference angle \( \phi = 45^{\circ} \). On a related note, when dealing with angles greater than \( 360^{\circ} \) or less than \( 0^{\circ} \), always bring them within the \( 0^{\circ} \) to \( 360^{\circ} \) range before calculating the reference angle. For example, \( 480^{\circ} \) can be simplified to \( 480^{\circ} - 360^{\circ} = 120^{\circ} \). From there, you would see that its reference angle would be \( 180^{\circ} - 120^{\circ} = 60^{\circ} \). It’s all about staying within the right boundaries!