The reference angle of the angle of -240º is of 60º.
The sine of the angle is given by:
[tex]\sin{-240^\circ} = \frac{\sqrt{3}}{2}[/tex]
The first step towards finding the equivalent angle of a negative angle is finding it's positive equivalent, adding 360º to it, hence:
-240º + 360º = 120º.
Then we have to find the equivalent on the first quadrant. 120º is on the second quadrant, hence:
180º - 120º = 60º.
The reference angle of the angle of -240º is of 60º.
On the second quadrant, the sine is positive, hence:
[tex]\sin{-240^\circ} = \sin{60^\circ} = \frac{\sqrt{3}}{2}[/tex]
More can be learned about reference angles at https://brainly.com/question/16884420
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