Given t = (-7π/9), the reference number of T is 2π/9.
How do we find the reference number of T?
The reference number for an angle in trigonometry is the acute angle that the terminal side of the given angle makes with the x-axis.
Reference angles are always between 0° and 90°,
They correspond to the same sine and cosine values as the original angle, but with the appropriate sign.
To find the reference number for each value of T:
t = (-7π/9)
Since T is negative, we find its positive equivalent:
The positive equivalent of the angle -7π/9 is 11π/9
the reference angle is 11π/9 - 9π/9 = 2π/9
Reference number = 2π/9