Reference angle,
When an angle is drawn on the coordinate plane with a vertex at the origin, the reference angle is the angle between the terminal side of the angle and the x-axis. The reference angle is always between 0 and 2π radians (or between 0 and 90 degrees).
angle: 255°
reference angle: 75°
Initial angle lies in 3rd quadrant.
now, let's calculate, sin(θ)
[tex]\begin{gathered} \sin\left(255^{\circ\:}\right)=-0.9659 \\ \sin\left(75^{\circ\:}\right)=0.9659 \end{gathered}[/tex]answer: Choice 'C'
